Question

If a - b = 4 and ab = -3, then what is the value of a3- b3?

A) 21 B) 28 C) 23 D) -20

Answer 1

Answer:

The answer is 28.

Step-by-step explanation:

We know that,

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

We are given that a - b = 4 and ab = -3.

Substituting these values in the equation,

$4^{3} = a^{3} -b^{3} -3(-3)(4)\\64=a^{3} -b^{3} +9(4)\\64=a^{3} -b^{3}+36\\a^{3} -b^{3}=64-36\\a^{3} -b^{3}=28$

∴The answer is 28.

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