Algebramedium · Past Paper

For what value of k are the roots of kx^2 + 4x + 1 = 0 real?

Ak ≤ 4
Bk ≥ 4
Ck = 4
Dk < 4

✓ Correct Answer: Ak ≤ 4

For real roots, D ≥ 0. 16 - 4k ≥ 0 => 4k ≤ 16 => k ≤ 4.

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