Question 37

If $$a^{3} + b^{3}$$ = 72 and ab = 8 , then what is the value of a + b?

Solution

$$(a+b)^{3} = a^{3}+ b^{3} + 3ab(a+b)$$

$$(a+b)^{3} = 72 + 3(8)(a+b)$$

we need to solve 3rd degree equation

so,without solving, by verification, a+b = 6,

so the answer is option C.

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