Question

If 3 is one of the roots of the quadratic equation kx² − 7x + 12 = 0, then k = ______.

Options

• 1

• −1

• 3

• −3

Answer 1

If 3 is one of the roots of the quadratic equation kx² − 7x + 12 = 0, then k = 1.

Explanation:

The given quadratic equation is kx² − 7x + 12 = 0

∴ Put x = 3

∴ k(3)² − 7(3) + 12 = 0

∴ 9k − 21 + 12 = 0

∴ 9k − 9 = 0

∴ 9k = 9

∴ k = `9/9`

∴ k = 1