Question

If x + y = 4, then find the value of x³ + y³ + 12xy – 64.

Answer 1

It is given that

x + y = 4

By cubing on both sides

(x + y)³ = 4³

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Expanding using formula

x³ + y³ + 3xy (x + y) = 64
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Substituting the value of x + y

x³ + y³ + 3xy (4) = 64
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So we get

x³ + y³ + 12xy – 64 = 0

Hence, the value of x³ + y³ + 12xy – 64 is 0.
( 0. 5 marks )