Which is the complete expansion of ( (x+7)^2 )?
Answer and explanation
Correct answer: \(x^2+14x+49\)
Using the identity \((a+b)^2=a^2+2ab+b^2\), put \(a=x\) and \(b=7\). Then \((x+7)^2=x^2+2\times x\times7+7^2=x^2+14x+49\). Hence, option A is correct. In option B, the middle term is written as \(7x\) instead of \(2ab=14x\). Exam tip: while expanding a squared binomial, always check the sign and coefficient of the \(2ab\) term.
Frequently asked questions
What is the correct answer to this question?
\(x^2+14x+49\)
Why is this the correct answer?
Using the identity \((a+b)^2=a^2+2ab+b^2\), put \(a=x\) and \(b=7\). Then \((x+7)^2=x^2+2\times x\times7+7^2=x^2+14x+49\). Hence, option A is correct. In option B, the middle term is written as \(7x\) instead of \(2ab=14x\). Exam tip: while expanding a squared binomial, always check the sign and coefficient of the \(2ab\) term.
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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