AM-282

Discriminant and nature of roots

A Math · Secondary 3 · Medium · Discriminant and nature of roots

For which values of

k

is the quadratic

x^2-4kx+9

always positive for all real

x

?

$-\dfrac{3}{2}<k<\dfrac{3}{2}$
$k>\dfrac{3}{2}$
$k< -\dfrac{3}{2}$
$k\le -\dfrac{3}{2} \text{ or } k\ge \dfrac{3}{2}$

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