If roots of quadratic equation x2 – kx + 4 = 0 then k will be(A) 2( – InterviewSolution

InterviewSolution

1.

If roots of quadratic equation x2 – kx + 4 = 0 then k will be(A) 2(B) 1(C) 4(D) 3

Answer»

Answer is (C) 4

Given equation x² – kx + 4 = 0

Comparing it with ax² + bx + c = 0

We get a = 1, b= -k and c = 4

D = b² – 4 ac = (-k)² – 4 × 1 × 4 = k² – 16

Roots are same

D = 0

⇒ k² – 16 = 0

⇒ k² = 16

⇒ k = ±√16

⇒ k = ± 4

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