Question

Find the product of following using suitable identities.(9x^3-7)(9x^3+7)

Answer 1

Solution :-

By using Identity :

→ ( x + a ) ( x + b ) = x² + ( a + b )x + ab

Here

• x = 9x³
• a = - 7
• b = 7

Substitute values in formula :

⇒ ( 9x³ )² + ( - 7 + 7 )9x³ + ( - 7 × 7 )

⇒ 81x⁶ + ( 0 )9x³ + ( - 49 )

⇒ 81x⁶ - 49