Question

expand the following (3a-7b)^2​

Answer 1

( 3a - 7b )²

[ Rule :- ( x - y )² = x² + y² - 2xy ]

= ( 3a )² + ( 7b )² - 2 ( 3a )(7b)

= 9a² + 49b² - 42ab

Answer 2

Step-by-step explanation:

$\: to \: expand = ({3a - 7b)}^{2} \\ \\ by \: the \: formulae \: ( {a - b)}^{2} = {a}^{2} + {b}^{2} - 2ab \\( {3a) }^{2} + ( {7b)}^{2} - 2 \times 3a \times 7b \\ = 9 {a }^{2} + 49 {b}^{2} - 42ab$