Question 87

# If a - b = -1 and ab = 6, then what is the value of $$a^{3} - b^{3}$$?

Solution

$$a^{3} - b^{3} = (a-b)^{3}+3(ab)(a-b)=(-1)^{3}+3(6)(-1)=-1-18=-19$$

so the answer is option B.