Question

20. (a + 2)^3 - (a - 2)3 can be simplified to:

a.2a^2 + 8a

b.8a^2 + 16.

c.12a + 16

d.12


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Answer 1

HEY MATE YOUR ANSWER IS HERE

WE WILL USE 2 IDENTITIES

( A + B )³ = A³ + B³ + 3AB( A + B)

( A - B )³ = A³ - B³ - 3AB( A - B)

NOW VALUE OF

( A + 2 )³ = A³ + 8 + 6A ( A + 2)

= A³ + 8 + 6A² + 12 A

( A - 2 )³ = A³ - 8 - 6A ( A - 2)

= A³ - 8 - 6A² + 12A

NOW PUT THEM IN

( A + 2 )³ - ( A - 2 )³

= ( A³ + 8 + 6A² + 12 A) - ( A³ - 8 - 6A² + 12A )

= A³ + 8 + 6A² + 12 A - A³ + 8 + 6A² - 12 A

= 12A² + 16

HENCE OPTION C IS CORRECT