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Which of the following trinomials represents the standard expansion of \((a+3b)^2\)?
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Answer and explanation
Correct answer: \(a^2+6ab+9b^2\)
With \(x=a,\ y=3b\), \((x+y)^2\) has middle term \(2(a)(3b)=6ab\) and last term \(9b^2\). So A is correct; D represents \((a-3b)^2\). Exam tip: check the middle-term sign.
Frequently asked questions
What is the correct answer to this question?
\(a^2+6ab+9b^2\)
Why is this the correct answer?
With \(x=a,\ y=3b\), \((x+y)^2\) has middle term \(2(a)(3b)=6ab\) and last term \(9b^2\). So A is correct; D represents \((a-3b)^2\). Exam tip: check the middle-term sign.
Which subject and chapter does this question cover?
This is a Class 9 Mathematics question. Chapter: Exploring Algebraic Identities. Topic: Algebraic identities.
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