Question

If one of the roots of quadratic equation x² + kx + 54 = 0 is – 6, then complete the following activity to find the value of ‘k’.

Activity: One of the roots of the quadratic equation x² + kx + 54 = 0 is – 6.

Therefore let’s take x = ______

(– 6)² + k(– 6) + 54 = 0

(______) – 6k + 54 = 0

– 6k + ______ = 0

k = ______

Answer 1

One of the roots of the quadratic equation x² + kx + 54 = 0 is – 6.

Therefore let’s take x = − 6

∴ (– 6)² + k(– 6) + 54 = 0

∴ 36 – 6k + 54 = 0

∴ – 6k + 90 = 0

∴ 6k = 90

∴ k = `90/6`

∴ k = 15