Question

If one zero of the quadratic polynomial x² + 3x + k is 2, then the value of k is ______.

Options

• 10

• –10

• –7

• –2

Answer 1

If one zero of the quadratic polynomial x² + 3x + k is 2, then the value of k is –10.

Explanation:

Let p(x) = x² + 3x + k

∵ 2 is a zero of p(x), then p(2) = 0

∴ (2)² + 3(2) + k = 0

⇒ 4 + 6 + k = 0

⇒ 10 + k = 0

⇒ k = –10