Question 52

If (a - b) = 4 and ab = 2, then $$(a^3 - b^3)$$ is equal to:

Solution

$$(a - b)^2 = a^2 + b^2 - 2ab$$

$$a^2 + b^2 = 16 + 4 = 20$$

$$(a^3 - b^3) = (a - b)(a^2 + ab + b^2)$$

= 4 (20 + 2) = 88

So, the answer would be option b)88.

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