Question

If a + b = 8 and ab = 15, find a³ + b³.

Answer 1

Here, a + b = 8, ab = 15

Using the identity,

a³ + b³ = (a + b)³ − 3ab (a + b)

= (8)³ − 3(15)(8)

= 512 − 3(120)

= 512 − 360

∴ a³ + b³ = 152