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For which of the following expressions is the identity for the difference of two perfect squares most appropriate for factorisation?
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Answer and explanation
Correct answer: \(25a^2-49b^2\)
Since \(25a^2=(5a)^2\) and \(49b^2=(7b)^2\), \(25a^2-49b^2=(5a-7b)(5a+7b)\). Option A is a perfect-square trinomial instead. Exam tip: first check whether both terms are perfect squares.
Frequently asked questions
What is the correct answer to this question?
\(25a^2-49b^2\)
Why is this the correct answer?
Since \(25a^2=(5a)^2\) and \(49b^2=(7b)^2\), \(25a^2-49b^2=(5a-7b)(5a+7b)\). Option A is a perfect-square trinomial instead. Exam tip: first check whether both terms are perfect squares.
Which subject and chapter does this question cover?
This is a Class 9 Mathematics question. Chapter: Exploring Algebraic Identities. Topic: Factorisation.
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