AM-376

Discriminant and nature of roots

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

The quadratic function is given by

y = x^2 - 4kx + 9

. For what value of

k

does the graph of

y

just touch the x-axis?

$k = \dfrac{3}{2}$ or $k = -\dfrac{3}{2}$
$k = \dfrac{9}{4}$ or $k = -\dfrac{9}{4}$
$k = 3$ or $k = -3$
$k = \dfrac{9}{2}$ or $k = -\dfrac{9}{2}$

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