Question

open the brackets and find the value of ab

Answer 1

Hope it will help u..

Answer 2

Identities used:

${(x + y)}^{2} = {x}^{2} + {y}^{2} + 2xy \\ {(x - y)}^{2} = {x}^{2} + {y}^{2} - 2xy$

$\frac{ {(6a - 5b)}^{2} - {(6a + 5b)}^{2} }{ab} = - 120$

So,

$\frac{( {(6a)}^{2} + {(5b)}^{2} - 2(6a)(5b)) - ( {(6a)}^{2} + {(5b)}^{2} + 2(6a)(5b))}{ab} = - 120 \\ \\ (36 {a}^{2} + 25 {b}^{2} - 30ab) -$

$36 {a}^{2} + 25 {b}^{2} - 60ab - 36 {a}^{2} - 25 {b}^{2} - 60ab) = - 120ab \\ \\ \bf \: Putting \: the \: like \: terms \\ \bf \: together \: we \: get \\ \\ 36 {a}^{2} - 36 {a}^{2} + 25 {b}^{2} - 25 {b}^{2} - 60ab - 60ab = - 120ab \\ \\ - 120ab = - 120ab \\ \\ = 0$