Question

If the equation kx² - 5x + k = 0 has real and equal roots, then

(A) 5/2

(B) -5/2

(C) ± 5/2

(D) √5/2

Answer 1

The correct answer is (C) ± 5/2.

The given equation is kx² - 5x + k = 0

Here, a = k, b = -5 and c = k

D = b² – 4ac

= (-5)² – 4 x k x k

= 25 – 4k²

The given equation will have real and equal roots, if

D = 0

25 – 4k² = 0

25 = 4k²

4k² = 25

k² = 25/4

k = √25/4

k = ± 5/2