Question

(a) Find the product using suitable identity.
(a + 3) (a -3) (a? + 9)​

Answer 1

Answer:

${a}^{4} - 81$

Step-by-step explanation:

$(a + 3)(a - 3)( {a}^{2} + 9) \\ = ( {a}^{2} - {3}^{2} )( {a}^{2} + 9) \\ = ( {a}^{2} - 9)( {a}^{2} + 9) \\ = (( {a}^{2} )^{2} - {9}^{2} ) \\ = {a}^{4} - 81$

$\small\mathbf\orange{Formula\:Used\::}$

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

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Answer 2

Question:-

$( a + 3)(a - 3)( {a}^{2} + 9) \\ \\ (a + b)(a - b) = {a}^{2} - {b}^{2} \\ \\ = ({a}^{2} - 9)( {a}^{2} + 9) \\ \\ = { ({a}^{2}) }^{2} - {9}^{2} \\ \\ = {a}^{4} - 81$