Practice
Composition of Functions Practice
Fifty original questions on inner-first evaluation, order, symbolic substitution, tables, ordered pairs, domains, and repeated application.
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Question 1
Explanation
First \(g(5)=-1\). Use that complete output as the input of \(f\): \(f(-1)=2(-1)+3=1\).
- Method
Calculate the inner output on a separate line, then feed it into the outer rule.
- Verified result
First \(g(5)=-1\). Use that complete output as the input of \(f\): \(f(-1)=2(-1)+3=1\).
Question 2
Explanation
First \(g(1)=-3\). Use that complete output as the input of \(f\): \(f(-3)=-3(-3)+2=11\).
- Method
Calculate the inner output on a separate line, then feed it into the outer rule.
- Verified result
First \(g(1)=-3\). Use that complete output as the input of \(f\): \(f(-3)=-3(-3)+2=11\).
Question 3
Explanation
First \(g(-2)=-4\). Use that complete output as the input of \(f\): \(f(-4)=4(-4)-1=-17\).
- Method
Calculate the inner output on a separate line, then feed it into the outer rule.
- Verified result
First \(g(-2)=-4\). Use that complete output as the input of \(f\): \(f(-4)=4(-4)-1=-17\).
Question 4
Explanation
First \(g(3)=-5\). Use that complete output as the input of \(f\): \(f(-5)=5(-5)+2=-23\).
- Method
Calculate the inner output on a separate line, then feed it into the outer rule.
- Verified result
First \(g(3)=-5\). Use that complete output as the input of \(f\): \(f(-5)=5(-5)+2=-23\).
Question 5
Explanation
First \(g(-1)=-1\). Use that complete output as the input of \(f\): \(f(-1)=2(-1)-4=-6\).
- Method
Calculate the inner output on a separate line, then feed it into the outer rule.
- Verified result
First \(g(-1)=-1\). Use that complete output as the input of \(f\): \(f(-1)=2(-1)-4=-6\).
Question 6
Explanation
The inner value is \(g(4)=7\). Substituting the entire result into the square gives \(f(7)=(7)^2+3=52\).
- Method
Use parentheses around the full inner result before applying a power.
- Verified result
The inner value is \(g(4)=7\). Substituting the entire result into the square gives \(f(7)=(7)^2+3=52\).
Question 7
Explanation
The inner value is \(g(-2)=5\). Substituting the entire result into the square gives \(f(5)=(5)^2-5=20\).
- Method
Use parentheses around the full inner result before applying a power.
- Verified result
The inner value is \(g(-2)=5\). Substituting the entire result into the square gives \(f(5)=(5)^2-5=20\).
Question 8
Explanation
The inner value is \(g(1)=5\). Substituting the entire result into the square gives \(f(5)=(5)^2+7=32\).
- Method
Use parentheses around the full inner result before applying a power.
- Verified result
The inner value is \(g(1)=5\). Substituting the entire result into the square gives \(f(5)=(5)^2+7=32\).
Question 9
Explanation
The inner value is \(g(3)=-10\). Substituting the entire result into the square gives \(f(-10)=(-10)^2+1=101\).
- Method
Use parentheses around the full inner result before applying a power.
- Verified result
The inner value is \(g(3)=-10\). Substituting the entire result into the square gives \(f(-10)=(-10)^2+1=101\).
Question 10
Explanation
The inner value is \(g(-1)=-3\). Substituting the entire result into the square gives \(f(-3)=(-3)^2-2=7\).
- Method
Use parentheses around the full inner result before applying a power.
- Verified result
The inner value is \(g(-1)=-3\). Substituting the entire result into the square gives \(f(-3)=(-3)^2-2=7\).
Question 11
Explanation
Replace every input in \(f\) with the complete expression \(g(x)\), then simplify. The resulting expression is \(3x+13\).
- Method
Write f with an empty input slot, insert g(x) in parentheses, and simplify only afterward.
- Verified result
Replace every input in \(f\) with the complete expression \(g(x)\), then simplify. The resulting expression is \(3x+13\).
Question 12
Explanation
Replace every input in \(f\) with the complete expression \(g(x)\), then simplify. The resulting expression is \(4x^2-4x+5\).
- Method
Write f with an empty input slot, insert g(x) in parentheses, and simplify only afterward.
- Verified result
Replace every input in \(f\) with the complete expression \(g(x)\), then simplify. The resulting expression is \(4x^2-4x+5\).
Question 13
Explanation
Replace every input in \(f\) with the complete expression \(g(x)\), then simplify. The resulting expression is \(3-x^2\).
- Method
Write f with an empty input slot, insert g(x) in parentheses, and simplify only afterward.
- Verified result
Replace every input in \(f\) with the complete expression \(g(x)\), then simplify. The resulting expression is \(3-x^2\).
Question 14
Explanation
Replace every input in \(f\) with the complete expression \(g(x)\), then simplify. The resulting expression is \(6x^2+7\).
- Method
Write f with an empty input slot, insert g(x) in parentheses, and simplify only afterward.
- Verified result
Replace every input in \(f\) with the complete expression \(g(x)\), then simplify. The resulting expression is \(6x^2+7\).
Question 15
Explanation
Replace every input in \(f\) with the complete expression \(g(x)\), then simplify. The resulting expression is \(x^2-8x+10\).
- Method
Write f with an empty input slot, insert g(x) in parentheses, and simplify only afterward.
- Verified result
Replace every input in \(f\) with the complete expression \(g(x)\), then simplify. The resulting expression is \(x^2-8x+10\).
Question 16
Explanation
Because \(g\) is outside, substitute the entire formula \(2x+1\) for every input of \(g\). Correct expansion gives \(4x^2+4x-2\).
- Method
Read from the innermost parentheses outward; the rightmost named function acts first.
- Verified result
Because \(g\) is outside, substitute the entire formula \(2x+1\) for every input of \(g\). Correct expansion gives \(4x^2+4x-2\).
Question 17
Explanation
Because \(g\) is outside, substitute the entire formula \(x-4\) for every input of \(g\). Correct expansion gives \(3x-10\).
- Method
Read from the innermost parentheses outward; the rightmost named function acts first.
- Verified result
Because \(g\) is outside, substitute the entire formula \(x-4\) for every input of \(g\). Correct expansion gives \(3x-10\).
Question 18
Explanation
Because \(g\) is outside, substitute the entire formula \(x^2+1\) for every input of \(g\). Correct expansion gives \(3-x^2\).
- Method
Read from the innermost parentheses outward; the rightmost named function acts first.
- Verified result
Because \(g\) is outside, substitute the entire formula \(x^2+1\) for every input of \(g\). Correct expansion gives \(3-x^2\).
Question 19
Explanation
Because \(g\) is outside, substitute the entire formula \(3x-5\) for every input of \(g\). Correct expansion gives \(18x^2-60x+50\).
- Method
Read from the innermost parentheses outward; the rightmost named function acts first.
- Verified result
Because \(g\) is outside, substitute the entire formula \(3x-5\) for every input of \(g\). Correct expansion gives \(18x^2-60x+50\).
Question 20
Explanation
Because \(g\) is outside, substitute the entire formula \(x+6\) for every input of \(g\). Correct expansion gives \(x^2+10x+24\).
- Method
Read from the innermost parentheses outward; the rightmost named function acts first.
- Verified result
Because \(g\) is outside, substitute the entire formula \(x+6\) for every input of \(g\). Correct expansion gives \(x^2+10x+24\).
Question 21
Explanation
Evaluating each pipeline independently gives \(f(g(4))=14\) and \(g(f(4))=18\). Their unequal values demonstrate that composition is generally order-dependent.
- Method
Draw two short arrows—g then f, and f then g—before calculating.
- Verified result
Evaluating each pipeline independently gives \(f(g(4))=14\) and \(g(f(4))=18\). Their unequal values demonstrate that composition is generally order-dependent.
Question 22
Explanation
Evaluating each pipeline independently gives \(f(g(3))=4\) and \(g(f(3))=8\). Their unequal values demonstrate that composition is generally order-dependent.
- Method
Draw two short arrows—g then f, and f then g—before calculating.
- Verified result
Evaluating each pipeline independently gives \(f(g(3))=4\) and \(g(f(3))=8\). Their unequal values demonstrate that composition is generally order-dependent.
Question 23
Explanation
Evaluating each pipeline independently gives \(f(g(-1))=-2\) and \(g(f(-1))=8\). Their unequal values demonstrate that composition is generally order-dependent.
- Method
Draw two short arrows—g then f, and f then g—before calculating.
- Verified result
Evaluating each pipeline independently gives \(f(g(-1))=-2\) and \(g(f(-1))=8\). Their unequal values demonstrate that composition is generally order-dependent.
Question 24
Explanation
Evaluating each pipeline independently gives \(f(g(2))=5\) and \(g(f(2))=15\). Their unequal values demonstrate that composition is generally order-dependent.
- Method
Draw two short arrows—g then f, and f then g—before calculating.
- Verified result
Evaluating each pipeline independently gives \(f(g(2))=5\) and \(g(f(2))=15\). Their unequal values demonstrate that composition is generally order-dependent.
Question 25
Explanation
Evaluating each pipeline independently gives \(f(g(-2))=6\) and \(g(f(-2))=-6\). Their unequal values demonstrate that composition is generally order-dependent.
- Method
Draw two short arrows—g then f, and f then g—before calculating.
- Verified result
Evaluating each pipeline independently gives \(f(g(-2))=6\) and \(g(f(-2))=-6\). Their unequal values demonstrate that composition is generally order-dependent.
Question 26
Explanation
Read the inner function's row first, then use that output as the input row for the outer function. The two-step lookup gives \(f(g(-2))=-2\).
- Method
Circle the inner output and locate it in the input column before making the second lookup.
- Verified result
Read the inner function's row first, then use that output as the input row for the outer function. The two-step lookup gives \(f(g(-2))=-2\).
Question 27
Explanation
Read the inner function's row first, then use that output as the input row for the outer function. The two-step lookup gives \(g(f(0))=3\).
- Method
Circle the inner output and locate it in the input column before making the second lookup.
- Verified result
Read the inner function's row first, then use that output as the input row for the outer function. The two-step lookup gives \(g(f(0))=3\).
Question 28
Explanation
Read the inner function's row first, then use that output as the input row for the outer function. The two-step lookup gives \(f(g(4))=0\).
- Method
Circle the inner output and locate it in the input column before making the second lookup.
- Verified result
Read the inner function's row first, then use that output as the input row for the outer function. The two-step lookup gives \(f(g(4))=0\).
Question 29
Explanation
Read the inner function's row first, then use that output as the input row for the outer function. The two-step lookup gives \(g(f(-2))=0\).
- Method
Circle the inner output and locate it in the input column before making the second lookup.
- Verified result
Read the inner function's row first, then use that output as the input row for the outer function. The two-step lookup gives \(g(f(-2))=0\).
Question 30
Explanation
Read the inner function's row first, then use that output as the input row for the outer function. The two-step lookup gives \(f(g(1))=1\).
- Method
Circle the inner output and locate it in the input column before making the second lookup.
- Verified result
Read the inner function's row first, then use that output as the input row for the outer function. The two-step lookup gives \(f(g(1))=1\).
Question 31
Explanation
Follow the ordered pair whose first coordinate matches the inner input, then use its second coordinate as the next input. This gives \(f(g(2))=5\).
- Method
Translate each ordered pair (input, output) into a lookup before composing.
- Verified result
Follow the ordered pair whose first coordinate matches the inner input, then use its second coordinate as the next input. This gives \(f(g(2))=5\).
Question 32
Explanation
Follow the ordered pair whose first coordinate matches the inner input, then use its second coordinate as the next input. This gives \(f(g(4))=6\).
- Method
Translate each ordered pair (input, output) into a lookup before composing.
- Verified result
Follow the ordered pair whose first coordinate matches the inner input, then use its second coordinate as the next input. This gives \(f(g(4))=6\).
Question 33
Explanation
Follow the ordered pair whose first coordinate matches the inner input, then use its second coordinate as the next input. This gives \(f(g(3))=1\).
- Method
Translate each ordered pair (input, output) into a lookup before composing.
- Verified result
Follow the ordered pair whose first coordinate matches the inner input, then use its second coordinate as the next input. This gives \(f(g(3))=1\).
Question 34
Explanation
Follow the ordered pair whose first coordinate matches the inner input, then use its second coordinate as the next input. This gives \(g(f(-4))=6\).
- Method
Translate each ordered pair (input, output) into a lookup before composing.
- Verified result
Follow the ordered pair whose first coordinate matches the inner input, then use its second coordinate as the next input. This gives \(g(f(-4))=6\).
Question 35
Explanation
Follow the ordered pair whose first coordinate matches the inner input, then use its second coordinate as the next input. This gives \(g(f(9))=-1\).
- Method
Translate each ordered pair (input, output) into a lookup before composing.
- Verified result
Follow the ordered pair whose first coordinate matches the inner input, then use its second coordinate as the next input. This gives \(g(f(9))=-1\).
Question 36
Explanation
The composition is undefined because the inner output is not accepted by f. A composition requires the original input to work in \(g\) and the resulting output to work as an input of \(f\).
- Method
Check the two domain gates in order: input into g, then g's output into f.
- Verified result
The composition is undefined because the inner output is not accepted by f. A composition requires the original input to work in \(g\) and the resulting output to work as an input of \(f\).
Question 37
Explanation
The composition is undefined at the first stage. A composition requires the original input to work in \(g\) and the resulting output to work as an input of \(f\).
- Method
Check the two domain gates in order: input into g, then g's output into f.
- Verified result
The composition is undefined at the first stage. A composition requires the original input to work in \(g\) and the resulting output to work as an input of \(f\).
Question 38
Explanation
The composition is defined and equals 9. A composition requires the original input to work in \(g\) and the resulting output to work as an input of \(f\).
- Method
Check the two domain gates in order: input into g, then g's output into f.
- Verified result
The composition is defined and equals 9. A composition requires the original input to work in \(g\) and the resulting output to work as an input of \(f\).
Question 39
Explanation
The composition is defined and equals -3. A composition requires the original input to work in \(g\) and the resulting output to work as an input of \(f\).
- Method
Check the two domain gates in order: input into g, then g's output into f.
- Verified result
The composition is defined and equals -3. A composition requires the original input to work in \(g\) and the resulting output to work as an input of \(f\).
Question 40
Explanation
The composition is undefined because the second lookup is missing. A composition requires the original input to work in \(g\) and the resulting output to work as an input of \(f\).
- Method
Check the two domain gates in order: input into g, then g's output into f.
- Verified result
The composition is undefined because the second lookup is missing. A composition requires the original input to work in \(g\) and the resulting output to work as an input of \(f\).
Question 41
Explanation
Apply the same function exactly 3 times, carrying each output into the next application. The final value is \(11\).
- Method
Write every intermediate output; do not multiply the number of applications by the first result.
- Verified result
Apply the same function exactly 3 times, carrying each output into the next application. The final value is \(11\).
Question 42
Explanation
Apply the same function exactly 3 times, carrying each output into the next application. The final value is \(24\).
- Method
Write every intermediate output; do not multiply the number of applications by the first result.
- Verified result
Apply the same function exactly 3 times, carrying each output into the next application. The final value is \(24\).
Question 43
Explanation
Apply the same function exactly 2 times, carrying each output into the next application. The final value is \(8\).
- Method
Write every intermediate output; do not multiply the number of applications by the first result.
- Verified result
Apply the same function exactly 2 times, carrying each output into the next application. The final value is \(8\).
Question 44
Explanation
Apply the same function exactly 3 times, carrying each output into the next application. The final value is \(4\).
- Method
Write every intermediate output; do not multiply the number of applications by the first result.
- Verified result
Apply the same function exactly 3 times, carrying each output into the next application. The final value is \(4\).
Question 45
Explanation
Apply the same function exactly 4 times, carrying each output into the next application. The final value is \(15\).
- Method
Write every intermediate output; do not multiply the number of applications by the first result.
- Verified result
Apply the same function exactly 4 times, carrying each output into the next application. The final value is \(15\).
Question 46
Explanation
The function nearest x is g, so g must be evaluated first. This restores the inner-first pipeline and both required domain checks.
- Method
Name the inner function and the intermediate output before judging a composition solution.
- Verified result
The function nearest x is g, so g must be evaluated first. This restores the inner-first pipeline and both required domain checks.
Question 47
Explanation
The circle denotes composition, not multiplication. This restores the inner-first pipeline and both required domain checks.
- Method
Name the inner function and the intermediate output before judging a composition solution.
- Verified result
The circle denotes composition, not multiplication. This restores the inner-first pipeline and both required domain checks.
Question 48
Explanation
Every occurrence of u must be replaced by the entire expression g(x). This restores the inner-first pipeline and both required domain checks.
- Method
Name the inner function and the intermediate output before judging a composition solution.
- Verified result
Every occurrence of u must be replaced by the entire expression g(x). This restores the inner-first pipeline and both required domain checks.
Question 49
Explanation
Composition is generally order-dependent, so both pipelines must be calculated. This restores the inner-first pipeline and both required domain checks.
- Method
Name the inner function and the intermediate output before judging a composition solution.
- Verified result
Composition is generally order-dependent, so both pipelines must be calculated. This restores the inner-first pipeline and both required domain checks.
Question 50
Explanation
The value 8 is only the inner output; without f(8), the composition is undefined. This restores the inner-first pipeline and both required domain checks.
- Method
Name the inner function and the intermediate output before judging a composition solution.
- Verified result
The value 8 is only the inner output; without f(8), the composition is undefined. This restores the inner-first pipeline and both required domain checks.
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Questions to review
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- Question 11Symbolic compositionEasy
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- Question 15Symbolic compositionEasy
- Question 16Reversed symbolic compositionMedium
- Question 17Reversed symbolic compositionMedium
- Question 18Reversed symbolic compositionMedium
- Question 19Reversed symbolic compositionMedium
- Question 20Reversed symbolic compositionMedium
- Question 21Comparing composition orderMedium
- Question 22Comparing composition orderMedium
- Question 23Comparing composition orderMedium
- Question 24Comparing composition orderMedium
- Question 25Comparing composition orderMedium
- Question 26Composition from a function tableMedium
- Question 27Composition from a function tableMedium
- Question 28Composition from a function tableMedium
- Question 29Composition from a function tableMedium
- Question 30Composition from a function tableMedium
- Question 31Composition from ordered pairsMedium
- Question 32Composition from ordered pairsMedium
- Question 33Composition from ordered pairsMedium
- Question 34Composition from ordered pairsMedium
- Question 35Composition from ordered pairsMedium
- Question 36Domain of a composite functionMedium
- Question 37Domain of a composite functionMedium
- Question 38Domain of a composite functionMedium
- Question 39Domain of a composite functionMedium
- Question 40Domain of a composite functionMedium
- Question 41Repeated function applicationHard
- Question 42Repeated function applicationHard
- Question 43Repeated function applicationHard
- Question 44Repeated function applicationHard
- Question 45Repeated function applicationHard
- Question 46Composition error analysisHard
- Question 47Composition error analysisHard
- Question 48Composition error analysisHard
- Question 49Composition error analysisHard
- Question 50Composition error analysisHard