Please tell this. Is am confused.
8a^3 - 64b^3 if 2a - 4b = 1 and ab = 2
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Answered by
10
I have answered n
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siddhartj724:
Thank you so much.
But why changed 3 into 24 in the third step
3(2a)(4b)=24ab and ab=2 .therefore 48
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Answered by
11
8a^3 - 64b^3 = (2a)^3 - (4b)^3
use identity:
a^3 - b^3 = (a - b) (a^2 + ab + b^2)
= (2a - 4b) [(2a)^2 + (2a)(4b) +(4b)^2]
= 1[ (2a - 4b)^2 + 2(2a)(4b) + 8ab)]
= (1)^2 + 24ab = 1 + 24(2)
= 49
Answer: 49
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