Question

39.Simplify using suitable identities:
(i) (3a + 9b) (3a - 9b)

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Answer 1

Step-by-step explanation:

(3a + 9b) (3a - 9b)

using identity

$(a + b)(a - b) = {a}^{2} - {b}^{2}$

this can be written as

${(3a)}^{2} - {(9b)}^{2} \\ 9 {a}^{2} - 81 {b}^{2}$

which is your answer