Question

Evaluate: 39^3 – 21^3 using the identity (a+b)3 – (a–b)3 = 2(b3 + 3a2b).

Answer 1

Step-by-step explanation:

(a+b)3=[(a+b)(a+b)] (a+b)=[a2+b2+2ab](a+b)

a(a2+b2+2ab)+b(a2+b2+2ab)

=a3+ab2+2(a2)b+(a2)b+b3+2a(b2)=a3+3a2b+3ab2+b3 = l.h.s

HENCE VERIFIED!

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Answer 2

Answer:

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