Question

Factorise 25x³y³-49xy

Answer 1

xy(25x^2y^2-49)= xy {(5xy+7) (5xy-7)}

Answer 2

$25 {x}^{3} {y}^{3} - 49xy \\ = xy(25 {x}^{2} {y}^{2} - 49) \\ = xy( \: {(5xy)}^{2} - {7}^{2} ) \\ = xy \: (5xy + 7)(5xy - 7)$
{ using the formula a^2-b^2=(a+b)(a-b)}
hope it helps you.