Find the least positive value of k for which the equation $x^{2} + k x + 4 = 0$ has real roots

k = 2

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k = 3

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k = 4

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k = 5

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Solution

The correct option is B $k = 4$
$x^{2} + k x + 4 = 0$
for real roots $D \geq 0$
$\Rightarrow k^{2} - 4 \times 4 \times 1 \geq 0 \Rightarrow k^{2} \geq 16$
$\Rightarrow k \geq 4$ C for positive valued

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