Simplify

Options
a) 2
b) 3
c) 5
d) 1

Solution

Let a = 4.2
b = 1.2
ab = 5.04
Formula :
a³ – b³ = (a-b) (a² +ab + b²)
= (a-b)
(a-b) = (4.2 – 1.2) = 3

Ans: 3