Question

If a − b = 7, ab = 30, find a³ − b³.

Answer 1

Here, a − b = 7, ab = 30

Using the identity,

a³ − b³ = (a − b)³ + 3ab(a − b)

= 7³ + 3 × 30 × 7

= 343 + 630

∴ a³ − b³ = 973