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Which of the following expressions is a difference of two perfect-square terms and can therefore be factorised using the identity \((a+b)(a-b)=a^2-b^2\)?
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Answer and explanation
Correct answer: \(49p^2-81q^2\)
\(49p^2=(7p)^2\) and \(81q^2=(9q)^2\). Hence, \(49p^2-81q^2=(7p+9q)(7p-9q)\). Option B is a sum, not a difference. In exams, check for two square terms with a minus sign between them.
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What is the correct answer to this question?
\(49p^2-81q^2\)
Why is this the correct answer?
\(49p^2=(7p)^2\) and \(81q^2=(9q)^2\). Hence, \(49p^2-81q^2=(7p+9q)(7p-9q)\). Option B is a sum, not a difference. In exams, check for two square terms with a minus sign between them.
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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