Question

4.If 2 is a root of the equation x^(2)+kx+12=0 find k. (a) 16 (b) -12 (c) 8 (d) -8​

Answer 1

Answer:

(d) -8

Explanation:

Given polynomial,

⇒ x² + kx + 12 = 0

Whose one of the roots is 2

We need to find the value of ‘k’

So, here x = 2

On substituting value of ‘x’ in the polynomial,

⇒ x² + kx + 12 = 0

⇒ (2)² + k(2) + 12 = 0

⇒ 4 + 2k + 12 = 0

⇒ 16 + 2k = 0

⇒ 2k = -16

⇒ k = -16/2

⇒ k = -8

∴ The value of ‘k’ is -8

_____________________

Quick check :-

Let's substitute the value of x and k in the polynomial,

⇒ x² + kx + 12 = 0

⇒ (2)² + (-8)(2) + 12 = 0

⇒ 4 - 16 + 12 = 0

⇒ 16 - 16 = 0

⇒ 0 = 0

∴ L. H. S. = R. H. S.