Question

Find the value of a^3 – 27b^3 , if a – 3b = -6 and ab = -10.

Answer 1

(a-b)^3=a^3-b^3-3ab(a-b)

(a-b)^3=a^3-(3b)^3-3ab(a-3b)

(-6)=a^3-(3b)^3-3(-10)(-6)

a^3-27b^3=(-216)+180

= -36