Question

If x = 3 is a root of the quadratic equation x² + kx − 8 = 0, then the value of k is ______.

Options

• −3

• 3

• `1/3`

• `-1/3`

Answer 1

If x = 3 is a root of the quadratic equation x² + kx − 8 = 0, then the value of k is `\underline(-1/3)`.

Explanation:

Given that x = 3 is a root of the quadratic equation:

x² + kx − 8 = 0

Substitute x = 3

(3)² + k(3) − 8 = 0

9 + 3k − 8 = 0

1 + 3k = 0

3k = −1

`k = -1/3`