Question

Find the following using suitable

identity (7x-9y)(7x-9y)

Answer 1

(7x - 9y)(7x - 9y)


By identity : (a - b)² = a² + b² - 2ab


(7x - 9y)²

(7x)² + (9y)² - 2(7x × 9y)

49x² + 81y² - 126xy

Answer 2

Hello friends!!

Here is your answer :-

$(7x - 9y)(7x - 9y)$

We can also write it as ( 7x - 9y)²

Method - 1

${(7x - 9y)}^{2}$

Using identity :-

( a - b)² = a² + b² - 2ab

(7x)² + (9y)² - 2(7x)(9y)

49x² + 81y² - 126xy.


Method - 2

( 7x - 9y) ( 7x - 9y)

= 7x ( 7x - 9y) - 9y ( 7x - 9y)

= 49x² - 63xy - 63xy + 81y²

= 49x² - 126xy + 81y²

Hope it helps you.. ^_^

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