Question
Find the value of k for which x2–4x+k=0 has coincident roots.
Answer: Option C
:
C
On comparing x2–4x+k=0 with standard form ax2+bx+c=0, we get
a = 1, b = -4 and c = k
Now, discriminant, D = b2−4ac
⇒D=(−4)2–4(1)k=16−4k
The roots of quadratic equation are co-incident only when D=0.
⇒16−4k=0
⇒k=4
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:
C
On comparing x2–4x+k=0 with standard form ax2+bx+c=0, we get
a = 1, b = -4 and c = k
Now, discriminant, D = b2−4ac
⇒D=(−4)2–4(1)k=16−4k
The roots of quadratic equation are co-incident only when D=0.
⇒16−4k=0
⇒k=4
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