Question

If a − b = 2, ab = 15, find a + b.

Answer 1

Here, a − b = 2, ab = 15,

Using the identity:

(a + b)² = (a − b)² + 4ab

(a + b)² = (2)² + 4(15)

(a + b)² = 4 + 60

(a + b)² = 64

a + b = `sqrt64`

∴ a + b = 8