MathChapter 2: Solving Linear Equations
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Prompt
What is a literal equation?
💡Many formulas are literal equations.
Answer
An equation containing two or more variables that expresses a general relationship.
Example\(d=rt\) relates distance, rate, and time.
Prompt
What is the target-variable mindset?
💡Solve only for the letter named.
Answer
Circle the requested variable and treat every other symbol as a constant while isolating it.
ExampleIn \(Ax+B=C\) for \(x\), \(A,B,C\) act like fixed numbers.
Prompt
Solve \(Ax+B=C\) for \(x\).
💡Subtract \(B\), then divide the complete side by \(A\).
Answer
\(x=(C-B)/A\), assuming \(A\ne0\).
ExampleDo not write \(C-B/A\), which divides only \(B\).
Prompt
Solve \(y=mx+b\) for \(x\).
💡Undo addition before multiplication.
Answer
\(x=(y-b)/m\), assuming \(m\ne0\).
ExampleFirst write \(y-b=mx\).
Prompt
Solve \(d=rt\) for \(t\).
💡Divide by the target's coefficient.
Answer
\(t=d/r\), assuming \(r\ne0\).
ExampleDistance divided by rate has units of time.
Prompt
How should a whole multi-term side be divided?
💡A fraction bar acts as grouping.
Answer
Keep the complete side grouped in one numerator or distribute the division to every term correctly.
Example\((P-2L)/2=P/2-L\).
Prompt
What should happen when the target appears in multiple terms?
💡Use the distributive property in reverse.
Answer
Collect all target terms on one side, then factor the target before dividing.
Prompt
Solve \(P=xr+xs\) for \(x\).
💡Factor \(x\) first.
Answer
\(x=P/(r+s)\), assuming \(r+s\ne0\).
Example\(P=x(r+s)\) is the key intermediate form.
Prompt
Solve \(ax+b=cx+d\) for \(x\).
💡Collect target terms and constants before factoring.
Answer
\(x=(d-b)/(a-c)\), provided \(a\ne c\).
Prompt
Why does \(a\ne c\) matter in \(x=(d-b)/(a-c)\)?
💡Never divide by zero.
Answer
The rearrangement divides by \(a-c\); if it is zero, the original equation must be classified as identity or no solution.
ExampleWhen \(a=c\), compare \(b\) and \(d\) instead.
Prompt
How do you isolate a target in a denominator?
💡Record original nonzero restrictions.
Answer
First multiply to clear the target-containing denominator, then isolate the resulting target product.
Example\(R=D/t\Rightarrow Rt=D\Rightarrow t=D/R\).
Prompt
Solve \(C=\frac59(F-32)\) for \(F\).
💡Undo the outside fraction before adding \(32\).
Answer
\(F=\frac95C+32\).
ExampleMultiply by \(9/5\), then add \(32\).
Prompt
Solve \(A=bh/2\) for \(h\).
💡Clear the denominator two first.
Answer
\(h=2A/b\), assuming \(b\ne0\).
Example\(2A=bh\Rightarrow h=2A/b\).
Prompt
Solve \(P=2L+2W\) for \(W\).
💡Subtract the non-target term, then divide the complete side.
Answer
\(W=(P-2L)/2=P/2-L\).
ExampleBoth displayed forms are equivalent.
Prompt
Why is a symbolic expression a complete answer?
💡Do not invent values.
Answer
Without numerical inputs, the task is to express the target's relationship to the other variables, not calculate a decimal.
ExampleSolving \(A=LW\) for \(W\) ends at \(W=A/L\).
Prompt
What restriction should be checked after a literal rearrangement?
💡Inspect the final fraction and original domain.
Answer
Any expression used as a denominator must be nonzero, along with restrictions from the original equation.
Example\(x=P/(r+s)\) requires \(r+s\ne0\).
Prompt
How do you solve a reciprocal formula for one denominator variable?
💡Do not invert a sum term by term.
Answer
Isolate its reciprocal, combine the other fractions, then take reciprocals with domain restrictions.
ExampleFrom \(1/f=1/u+1/v\), isolate \(1/v\) first.
Prompt
What common error occurs after factoring \(x(a+b)=M\)?
💡The parentheses form one coefficient.
Answer
Dividing by only \(a\) or \(b\) instead of the complete factor \(a+b\).
ExampleThe correct result is \(x=M/(a+b)\).
Prompt
What is a reliable workflow for a complex literal equation?
💡Keep target-containing structure visible.
Answer
Name the target, simplify, collect target terms, factor if needed, divide by the full coefficient, and audit restrictions.
ExampleUse this on \(A=p(x+r)-q(x-s)\).
Prompt
How can you audit a rearranged formula?
💡Check grouping, signs, and units.
Answer
Reverse the operations or substitute the rearranged target expression into the original structure and simplify.
ExampleSubstituting \(t=d/r\) into \(d=rt\) returns \(d=d\).
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