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Question
For what values of k, the roots of the equation x2 + 4x +k = 0 are real?
Solution
x2 +4x +k=0
∴ Roots of given equation are real,
D≥0
implies that
(4)2 - 4 ×k ≥ 0
implies that
-4k ≥ -16
implies that
k ≤ 4
∴ k has all real values k ≤ 4.
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