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Question
Find the value of x3 + y3 – 12xy + 64, when x + y = – 4
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Solution
Here, we see that, x + y + 4 = 0
∴ x3 + y3 + (4)3 = 3xy(4) ...[Using identity, a + b + c = 0, then a3 + b3 + c3 = 3abc]
= 12xy ...(i)
Now, x3 + y3 – 12xy + 64 = x3 + y3 + 64 – 12xy
= 12xy – 12xy ...[From equation (i)]
= 0
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