Question

factorise :49a^2 - 225b^2

Answer 1

$49 {a}^{2} - 225 {b}^{2}$
$= {(7a)}^{2} - {(15b)}^{2}$
$= (7a + 15b)(7a - 15b) \: \\ as \\ {a}^{2} - {b}^{2} = ( a + b)(a - b)$