JAMB 2010 · UTME · Q42

At what value of $x$ does the function $y = -3 - 2x + x^2$ attain a minimum value?

Worked solution (try it first)

At a turning point $\frac{dy}{dx} = 0$ : $-2 + 2x = 0$ , so $x = 1$ .
$\frac{d^2y}{dx^2} = 2 > 0$ , so it is a minimum.
So $x = 1$ , option A.

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