Question

factorise this problem 25a-9b

Answer 1

the sum seems missing the squares of a and b.
the sum should have been something like this.
25a^2-9b^2
= (5a)^2 - (3b)^2
= (5a+3b)(5a-3b)

Answer 2

$25a^2-9b^2 \\ = 5a^2 - 3b^2 \\ = (5a+3b)(5a-3b)$