Question

Factorise: $25a^2-36b^2$

• A. (5a - 6b)(5a + 6b)
• B. (5a - 6b)(5a - 6b)
• C. (5a + 6b)(5a + 6b)
• D. (6b - 5a)(6b + 5a)

Answer 1

The correct option is B (5a - 6b)(5a - 6b)

The given expression is $25a^2-36b^2$
= $(5a{)}^2-(6b{)}^2$
= $(5a-6b)(5a+6b)$
[Using the identity $a^2-b^2=(a+b)(a-b)$]

Hence, $25a^2-36b^2$ = $(5a-6b)(5a+6b)$