Question

If a – b = 9, ab = 10, find a³ – b³.

Answer 1

Here, a – b = 9, ab = 10,

Using the identity,

a³ − b³ = (a − b)³ − 3ab(a − b)

= 9³ + 3 × 10 × 9

= 729 + 270

∴ a³ − b³ = 999