Question

(7x-9).(7x+9) is equal to ​

Answer 1

Answer:

$(7x - 9)(7x + 9) \\ \\ using \: formula \\ \\ (a + b)(a - b) \\ \\ = {a}^{2} - {b}^{2} \\ \\ here \: a = 7x \\ and \: b = 9 \\ \\ so \: ( {7x)}^{2} - {(9)}^{2} \\ \\ = 49 {x}^{2} - 81$

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Answer 2

Answer:

$(x - y)(x + y) = ( {x}^{2} - {y}^{2} ) \\ (7x - 9)(7x + 9) = ( ({7x})^{2} - {9}^{2} ) \\ = 49 {x}^{2} - 81$