Question

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

(a) 10 

(b) -10 

(c) 5 

(d) -5

Answer 1

(b) -10 

Let f(x) = x² + 3x + k

∵ 2 is zero of f(x)

∴ f (2) = 0

⇒ 2² + 3 x 2 + k = 0

⇒ k = -4 -6 = -10