Practice
Recursive Formula Practice
Fifty original questions on initial conditions, indexing, additive and multiplicative recurrences, function iteration, real-world models, tables, and error analysis.
- Answered
- 0 / 50
- Correct
- 0
- Incorrect
- 0
- Accuracy
- 0%
Question 1
Explanation
The standalone stated term \(a_0=7\) fixes where the sequence begins. The remaining equation tells how later terms depend on earlier ones.
- Method
Separate the one stated term from the equation containing a previous-term subscript.
- Verified result
The standalone stated term \(a_0=7\) fixes where the sequence begins. The remaining equation tells how later terms depend on earlier ones.
Question 2
Explanation
The standalone stated term \(b_1=-3\) fixes where the sequence begins. The remaining equation tells how later terms depend on earlier ones.
- Method
Separate the one stated term from the equation containing a previous-term subscript.
- Verified result
The standalone stated term \(b_1=-3\) fixes where the sequence begins. The remaining equation tells how later terms depend on earlier ones.
Question 3
Explanation
The standalone stated term \(c_4=10\) fixes where the sequence begins. The remaining equation tells how later terms depend on earlier ones.
- Method
Separate the one stated term from the equation containing a previous-term subscript.
- Verified result
The standalone stated term \(c_4=10\) fixes where the sequence begins. The remaining equation tells how later terms depend on earlier ones.
Question 4
Explanation
The standalone stated term \(d_0=5\) fixes where the sequence begins. The remaining equation tells how later terms depend on earlier ones.
- Method
Separate the one stated term from the equation containing a previous-term subscript.
- Verified result
The standalone stated term \(d_0=5\) fixes where the sequence begins. The remaining equation tells how later terms depend on earlier ones.
Question 5
Explanation
The standalone stated term \(p_2=12\) fixes where the sequence begins. The remaining equation tells how later terms depend on earlier ones.
- Method
Separate the one stated term from the equation containing a previous-term subscript.
- Verified result
The standalone stated term \(p_2=12\) fixes where the sequence begins. The remaining equation tells how later terms depend on earlier ones.
Question 6
Explanation
Calculate every term in order: \(a_1=6+5=11,\ a_2=11+5=16\). Therefore \(a_2=16\).
- Method
Count the number of index steps from the given term to the requested term, updating the previous value each time.
- Verified result
Calculate every term in order: \(a_1=6+5=11,\ a_2=11+5=16\). Therefore \(a_2=16\).
Question 7
Explanation
Calculate every term in order: \(a_2=-4+7=3,\ a_3=3+7=10\). Therefore \(a_3=10\).
- Method
Count the number of index steps from the given term to the requested term, updating the previous value each time.
- Verified result
Calculate every term in order: \(a_2=-4+7=3,\ a_3=3+7=10\). Therefore \(a_3=10\).
Question 8
Explanation
Calculate every term in order: \(a_1=12-3=9,\ a_2=9-3=6,\ a_3=6-3=3\). Therefore \(a_3=3\).
- Method
Count the number of index steps from the given term to the requested term, updating the previous value each time.
- Verified result
Calculate every term in order: \(a_1=12-3=9,\ a_2=9-3=6,\ a_3=6-3=3\). Therefore \(a_3=3\).
Question 9
Explanation
Calculate every term in order: \(a_3=9+4=13,\ a_4=13+4=17\). Therefore \(a_4=17\).
- Method
Count the number of index steps from the given term to the requested term, updating the previous value each time.
- Verified result
Calculate every term in order: \(a_3=9+4=13,\ a_4=13+4=17\). Therefore \(a_4=17\).
Question 10
Explanation
Calculate every term in order: \(a_2=15-6=9,\ a_3=9-6=3,\ a_4=3-6=-3\). Therefore \(a_4=-3\).
- Method
Count the number of index steps from the given term to the requested term, updating the previous value each time.
- Verified result
Calculate every term in order: \(a_2=15-6=9,\ a_3=9-6=3,\ a_4=3-6=-3\). Therefore \(a_4=-3\).
Question 11
Explanation
There are \(3\) recursive steps. Multiplying the current term by \(2\) at each step gives \(u_3=24\).
- Method
Mark each index above the term so a zero-based sequence does not lose or gain a multiplication.
- Verified result
There are \(3\) recursive steps. Multiplying the current term by \(2\) at each step gives \(u_3=24\).
Question 12
Explanation
There are \(2\) recursive steps. Multiplying the current term by \(3\) at each step gives \(u_3=45\).
- Method
Mark each index above the term so a zero-based sequence does not lose or gain a multiplication.
- Verified result
There are \(2\) recursive steps. Multiplying the current term by \(3\) at each step gives \(u_3=45\).
Question 13
Explanation
There are \(3\) recursive steps. Multiplying the current term by \(0.5\) at each step gives \(u_3=8\).
- Method
Mark each index above the term so a zero-based sequence does not lose or gain a multiplication.
- Verified result
There are \(3\) recursive steps. Multiplying the current term by \(0.5\) at each step gives \(u_3=8\).
Question 14
Explanation
There are \(3\) recursive steps. Multiplying the current term by \(-2\) at each step gives \(u_5=16\).
- Method
Mark each index above the term so a zero-based sequence does not lose or gain a multiplication.
- Verified result
There are \(3\) recursive steps. Multiplying the current term by \(-2\) at each step gives \(u_5=16\).
Question 15
Explanation
There are \(3\) recursive steps. Multiplying the current term by \(0.3333333333333333\) at each step gives \(u_4=3\).
- Method
Mark each index above the term so a zero-based sequence does not lose or gain a multiplication.
- Verified result
There are \(3\) recursive steps. Multiplying the current term by \(0.3333333333333333\) at each step gives \(u_4=3\).
Question 16
Explanation
Use both the current index and the immediately preceding value at each step: \(a_1=4,\ a_2=8,\ a_3=14\). Thus the requested term is \(14\).
- Method
Write the current n beside every substitution so the n-dependent term changes at the correct time.
- Verified result
Use both the current index and the immediately preceding value at each step: \(a_1=4,\ a_2=8,\ a_3=14\). Thus the requested term is \(14\).
Question 17
Explanation
Use both the current index and the immediately preceding value at each step: \(a_2=6,\ a_3=9,\ a_4=14\). Thus the requested term is \(14\).
- Method
Write the current n beside every substitution so the n-dependent term changes at the correct time.
- Verified result
Use both the current index and the immediately preceding value at each step: \(a_2=6,\ a_3=9,\ a_4=14\). Thus the requested term is \(14\).
Question 18
Explanation
Use both the current index and the immediately preceding value at each step: \(a_1=0,\ a_2=4,\ a_3=13\). Thus the requested term is \(13\).
- Method
Write the current n beside every substitution so the n-dependent term changes at the correct time.
- Verified result
Use both the current index and the immediately preceding value at each step: \(a_1=0,\ a_2=4,\ a_3=13\). Thus the requested term is \(13\).
Question 19
Explanation
Use both the current index and the immediately preceding value at each step: \(a_3=18,\ a_4=58,\ a_5=179\). Thus the requested term is \(179\).
- Method
Write the current n beside every substitution so the n-dependent term changes at the correct time.
- Verified result
Use both the current index and the immediately preceding value at each step: \(a_3=18,\ a_4=58,\ a_5=179\). Thus the requested term is \(179\).
Question 20
Explanation
Use both the current index and the immediately preceding value at each step: \(a_2=14,\ a_3=5,\ a_4=-7\). Thus the requested term is \(-7\).
- Method
Write the current n beside every substitution so the n-dependent term changes at the correct time.
- Verified result
Use both the current index and the immediately preceding value at each step: \(a_2=14,\ a_3=5,\ a_4=-7\). Thus the requested term is \(-7\).
Question 21
Explanation
The consecutive outputs are \(5,\ 9,\ 13,\ 17\). Each output becomes the next input, so the final result is \(17\).
- Method
Treat repeated composition as a recursion: record every intermediate function value.
- Verified result
The consecutive outputs are \(5,\ 9,\ 13,\ 17\). Each output becomes the next input, so the final result is \(17\).
Question 22
Explanation
The consecutive outputs are \(4,\ 10,\ 28\). Each output becomes the next input, so the final result is \(28\).
- Method
Treat repeated composition as a recursion: record every intermediate function value.
- Verified result
The consecutive outputs are \(4,\ 10,\ 28\). Each output becomes the next input, so the final result is \(28\).
Question 23
Explanation
The consecutive outputs are \(2,\ 5,\ 26\). Each output becomes the next input, so the final result is \(26\).
- Method
Treat repeated composition as a recursion: record every intermediate function value.
- Verified result
The consecutive outputs are \(2,\ 5,\ 26\). Each output becomes the next input, so the final result is \(26\).
Question 24
Explanation
The consecutive outputs are \(7,\ 3,\ 7,\ 3\). Each output becomes the next input, so the final result is \(3\).
- Method
Treat repeated composition as a recursion: record every intermediate function value.
- Verified result
The consecutive outputs are \(7,\ 3,\ 7,\ 3\). Each output becomes the next input, so the final result is \(3\).
Question 25
Explanation
The consecutive outputs are \(1,\ 5,\ 13,\ 29\). Each output becomes the next input, so the final result is \(29\).
- Method
Treat repeated composition as a recursion: record every intermediate function value.
- Verified result
The consecutive outputs are \(1,\ 5,\ 13,\ 29\). Each output becomes the next input, so the final result is \(29\).
Question 26
Explanation
Apply the recurrence 2 times, multiplying the previous balance before adding the contribution. Keeping full precision gives \(A_2=913.12\).
- Method
Store the unrounded calculator result from each period and add the fixed contribution after multiplication.
- Verified result
Apply the recurrence 2 times, multiplying the previous balance before adding the contribution. Keeping full precision gives \(A_2=913.12\).
Question 27
Explanation
Apply the recurrence 3 times, multiplying the previous balance before adding the contribution. Keeping full precision gives \(A_3=1742.41\).
- Method
Store the unrounded calculator result from each period and add the fixed contribution after multiplication.
- Verified result
Apply the recurrence 3 times, multiplying the previous balance before adding the contribution. Keeping full precision gives \(A_3=1742.41\).
Question 28
Explanation
Apply the recurrence 2 times, multiplying the previous balance before adding the contribution. Keeping full precision gives \(A_2=2624.56\).
- Method
Store the unrounded calculator result from each period and add the fixed contribution after multiplication.
- Verified result
Apply the recurrence 2 times, multiplying the previous balance before adding the contribution. Keeping full precision gives \(A_2=2624.56\).
Question 29
Explanation
Apply the recurrence 3 times, multiplying the previous balance before adding the contribution. Keeping full precision gives \(A_3=732.91\).
- Method
Store the unrounded calculator result from each period and add the fixed contribution after multiplication.
- Verified result
Apply the recurrence 3 times, multiplying the previous balance before adding the contribution. Keeping full precision gives \(A_3=732.91\).
Question 30
Explanation
Apply the recurrence 2 times, multiplying the previous balance before adding the contribution. Keeping full precision gives \(A_2=3457.92\).
- Method
Store the unrounded calculator result from each period and add the fixed contribution after multiplication.
- Verified result
Apply the recurrence 2 times, multiplying the previous balance before adding the contribution. Keeping full precision gives \(A_2=3457.92\).
Question 31
Explanation
The recurrence is \(I_n=0.8I_{n-1}+70\). Repeating it with each newly computed stock gives \(I_2=446\).
- Method
Translate “retains, then adds” in that exact order; parentheses would be required for the reverse order.
- Verified result
The recurrence is \(I_n=0.8I_{n-1}+70\). Repeating it with each newly computed stock gives \(I_2=446\).
Question 32
Explanation
The recurrence is \(I_n=0.75I_{n-1}+30\). Repeating it with each newly computed stock gives \(I_3=170.63\).
- Method
Translate “retains, then adds” in that exact order; parentheses would be required for the reverse order.
- Verified result
The recurrence is \(I_n=0.75I_{n-1}+30\). Repeating it with each newly computed stock gives \(I_3=170.63\).
Question 33
Explanation
The recurrence is \(I_n=0.9I_{n-1}+12\). Repeating it with each newly computed stock gives \(I_2=120\).
- Method
Translate “retains, then adds” in that exact order; parentheses would be required for the reverse order.
- Verified result
The recurrence is \(I_n=0.9I_{n-1}+12\). Repeating it with each newly computed stock gives \(I_2=120\).
Question 34
Explanation
The recurrence is \(I_n=0.85I_{n-1}+45\). Repeating it with each newly computed stock gives \(I_3=361.41\).
- Method
Translate “retains, then adds” in that exact order; parentheses would be required for the reverse order.
- Verified result
The recurrence is \(I_n=0.85I_{n-1}+45\). Repeating it with each newly computed stock gives \(I_3=361.41\).
Question 35
Explanation
The recurrence is \(I_n=0.6I_{n-1}+90\). Repeating it with each newly computed stock gives \(I_2=252\).
- Method
Translate “retains, then adds” in that exact order; parentheses would be required for the reverse order.
- Verified result
The recurrence is \(I_n=0.6I_{n-1}+90\). Repeating it with each newly computed stock gives \(I_2=252\).
Question 36
Explanation
Use the term immediately before the concealed row in \(a_n=2a_{n-1}+3\). Substitution produces \(a_2=25\), which also leads consistently to the next visible term.
- Method
Use both neighboring rows when available: compute forward, then verify the following row.
- Verified result
Use the term immediately before the concealed row in \(a_n=2a_{n-1}+3\). Substitution produces \(a_2=25\), which also leads consistently to the next visible term.
Question 37
Explanation
Use the term immediately before the concealed row in \(a_n=0.5a_{n-1}+2\). Substitution produces \(a_3=14.75\), which also leads consistently to the next visible term.
- Method
Use both neighboring rows when available: compute forward, then verify the following row.
- Verified result
Use the term immediately before the concealed row in \(a_n=0.5a_{n-1}+2\). Substitution produces \(a_3=14.75\), which also leads consistently to the next visible term.
Question 38
Explanation
Use the term immediately before the concealed row in \(a_n=3a_{n-1}+7\). Substitution produces \(a_1=1\), which also leads consistently to the next visible term.
- Method
Use both neighboring rows when available: compute forward, then verify the following row.
- Verified result
Use the term immediately before the concealed row in \(a_n=3a_{n-1}+7\). Substitution produces \(a_1=1\), which also leads consistently to the next visible term.
Question 39
Explanation
Use the term immediately before the concealed row in \(a_n=2a_{n-1}-2\). Substitution produces \(a_2=18\), which also leads consistently to the next visible term.
- Method
Use both neighboring rows when available: compute forward, then verify the following row.
- Verified result
Use the term immediately before the concealed row in \(a_n=2a_{n-1}-2\). Substitution produces \(a_2=18\), which also leads consistently to the next visible term.
Question 40
Explanation
Use the term immediately before the concealed row in \(a_n=0.8a_{n-1}+2\). Substitution produces \(a_1=82\), which also leads consistently to the next visible term.
- Method
Use both neighboring rows when available: compute forward, then verify the following row.
- Verified result
Use the term immediately before the concealed row in \(a_n=0.8a_{n-1}+2\). Substitution produces \(a_1=82\), which also leads consistently to the next visible term.
Question 41
Explanation
Substituting consecutive terms into \(a_1=3 and a_n=2a_{n-1}+2\) reproduces the full list and preserves the stated starting index. Each alternative fails either a transition or the index.
- Method
Test a proposed rule on at least two transitions and verify its initial-condition index.
- Verified result
Substituting consecutive terms into \(a_1=3 and a_n=2a_{n-1}+2\) reproduces the full list and preserves the stated starting index. Each alternative fails either a transition or the index.
Question 42
Explanation
Substituting consecutive terms into \(a_0=64 and a_n=0.5a_{n-1}+2\) reproduces the full list and preserves the stated starting index. Each alternative fails either a transition or the index.
- Method
Test a proposed rule on at least two transitions and verify its initial-condition index.
- Verified result
Substituting consecutive terms into \(a_0=64 and a_n=0.5a_{n-1}+2\) reproduces the full list and preserves the stated starting index. Each alternative fails either a transition or the index.
Question 43
Explanation
Substituting consecutive terms into \(a_2=5 and a_n=2a_{n-1}+3\) reproduces the full list and preserves the stated starting index. Each alternative fails either a transition or the index.
- Method
Test a proposed rule on at least two transitions and verify its initial-condition index.
- Verified result
Substituting consecutive terms into \(a_2=5 and a_n=2a_{n-1}+3\) reproduces the full list and preserves the stated starting index. Each alternative fails either a transition or the index.
Question 44
Explanation
Substituting consecutive terms into \(a_1=10 and a_n=a_{n-1}-3(n-1)\) reproduces the full list and preserves the stated starting index. Each alternative fails either a transition or the index.
- Method
Test a proposed rule on at least two transitions and verify its initial-condition index.
- Verified result
Substituting consecutive terms into \(a_1=10 and a_n=a_{n-1}-3(n-1)\) reproduces the full list and preserves the stated starting index. Each alternative fails either a transition or the index.
Question 45
Explanation
Substituting consecutive terms into \(a_0=2 and a_n=(n+2)a_{n-1}\) reproduces the full list and preserves the stated starting index. Each alternative fails either a transition or the index.
- Method
Test a proposed rule on at least two transitions and verify its initial-condition index.
- Verified result
Substituting consecutive terms into \(a_0=2 and a_n=(n+2)a_{n-1}\) reproduces the full list and preserves the stated starting index. Each alternative fails either a transition or the index.
Question 46
Explanation
Each step must use the newly calculated previous term, not the initial value again. Recursive work must preserve the initial index, every intermediate state, and the operation order written in the rule.
- Method
Audit the index, previous value, and operations as three separate checkpoints.
- Verified result
Each step must use the newly calculated previous term, not the initial value again. Recursive work must preserve the initial index, every intermediate state, and the operation order written in the rule.
Question 47
Explanation
The term immediately after a_0 is a_1, so the work has an index shift. Recursive work must preserve the initial index, every intermediate state, and the operation order written in the rule.
- Method
Audit the index, previous value, and operations as three separate checkpoints.
- Verified result
The term immediately after a_0 is a_1, so the work has an index shift. Recursive work must preserve the initial index, every intermediate state, and the operation order written in the rule.
Question 48
Explanation
The formula multiplies the previous amount first and adds 50 afterward. Recursive work must preserve the initial index, every intermediate state, and the operation order written in the rule.
- Method
Audit the index, previous value, and operations as three separate checkpoints.
- Verified result
The formula multiplies the previous amount first and adds 50 afterward. Recursive work must preserve the initial index, every intermediate state, and the operation order written in the rule.
Question 49
Explanation
The current index n changes, so the squared addition must change with each term. Recursive work must preserve the initial index, every intermediate state, and the operation order written in the rule.
- Method
Audit the index, previous value, and operations as three separate checkpoints.
- Verified result
The current index n changes, so the squared addition must change with each term. Recursive work must preserve the initial index, every intermediate state, and the operation order written in the rule.
Question 50
Explanation
Intermediate rounding can accumulate error; retain precision until the requested final rounding. Recursive work must preserve the initial index, every intermediate state, and the operation order written in the rule.
- Method
Audit the index, previous value, and operations as three separate checkpoints.
- Verified result
Intermediate rounding can accumulate error; retain precision until the requested final rounding. Recursive work must preserve the initial index, every intermediate state, and the operation order written in the rule.
Keyboard: use Tab to move, arrow keys to change answer choices, and Enter to check an answer.
Your practice summary
Use the results to decide what to review before your next attempt.
- Correct
- 0
- Incorrect
- 0
- Completed
- 50 / 50
Questions to review
No mistakes this time. Excellent work.
- Question 1Identifying an initial conditionEasy
- Question 2Identifying an initial conditionEasy
- Question 3Identifying an initial conditionEasy
- Question 4Identifying an initial conditionEasy
- Question 5Identifying an initial conditionEasy
- Question 6Additive recurrenceEasy
- Question 7Additive recurrenceEasy
- Question 8Additive recurrenceEasy
- Question 9Additive recurrenceEasy
- Question 10Additive recurrenceEasy
- Question 11Multiplicative recurrenceEasy
- Question 12Multiplicative recurrenceEasy
- Question 13Multiplicative recurrenceEasy
- Question 14Multiplicative recurrenceEasy
- Question 15Multiplicative recurrenceEasy
- Question 16Index-dependent recurrenceMedium
- Question 17Index-dependent recurrenceMedium
- Question 18Index-dependent recurrenceMedium
- Question 19Index-dependent recurrenceMedium
- Question 20Index-dependent recurrenceMedium
- Question 21Repeated function recursionMedium
- Question 22Repeated function recursionMedium
- Question 23Repeated function recursionMedium
- Question 24Repeated function recursionMedium
- Question 25Repeated function recursionMedium
- Question 26Financial recurrenceMedium
- Question 27Financial recurrenceMedium
- Question 28Financial recurrenceMedium
- Question 29Financial recurrenceMedium
- Question 30Financial recurrenceMedium
- Question 31Inventory recurrenceMedium
- Question 32Inventory recurrenceMedium
- Question 33Inventory recurrenceMedium
- Question 34Inventory recurrenceMedium
- Question 35Inventory recurrenceMedium
- Question 36Completing a recursive tableMedium
- Question 37Completing a recursive tableMedium
- Question 38Completing a recursive tableMedium
- Question 39Completing a recursive tableMedium
- Question 40Completing a recursive tableMedium
- Question 41Recognizing a recursive ruleHard
- Question 42Recognizing a recursive ruleHard
- Question 43Recognizing a recursive ruleHard
- Question 44Recognizing a recursive ruleHard
- Question 45Recognizing a recursive ruleHard
- Question 46Recursive error analysisHard
- Question 47Recursive error analysisHard
- Question 48Recursive error analysisHard
- Question 49Recursive error analysisHard
- Question 50Recursive error analysisHard