Question

If 4 is a root of equation x² + kx – 4 = 0; the value of k is ______.

Options

• 3

• –3

• 2

• –2

Answer 1

If 4 is a root of equation x² + kx – 4 = 0; the value of k is –3.

Explanation:

Given 4 is a root of equation

x² + kx – 4 = 0   ...(1)

∴ 4 satisfies given equation (1)

∴ 4² + k × 4 – 4 = 0

`\implies` 16 + 4k – 4 = 0

`\implies` 12 + 4k = 0

`\implies` 4k = – 12

`\implies` k = – 3