A student writes \((3x+2)^2\) as \(9x^2+4\). Which is the correct quadratic expression after correcting the error?
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Answer and explanation
Correct answer: \(9x^2+12x+4\)
Using \((a+b)^2=a^2+2ab+b^2\), take \(a=3x\) and \(b=2\). The missing middle term is \(2\times3x\times2=12x\), so the expression is \(9x^2+12x+4\). Exam tip: always check the \(2ab\) term.
Frequently asked questions
What is the correct answer to this question?
\(9x^2+12x+4\)
Why is this the correct answer?
Using \((a+b)^2=a^2+2ab+b^2\), take \(a=3x\) and \(b=2\). The missing middle term is \(2\times3x\times2=12x\), so the expression is \(9x^2+12x+4\). Exam tip: always check the \(2ab\) term.
Which subject and chapter does this question cover?
This is a Class 9 Mathematics question. Chapter: Exploring Algebraic Identities. Topic: Quadratic expressions.
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