JAMB 2016 · UTME · Q17

What value of $x$ will make the function $x(4 - x)$ a maximum?

Worked solution (try it first)

Expand: $x(4 - x) = 4x - x^2$ .
At the maximum the gradient is zero: $4 - 2x = 0$ , so $x = 2$ .
The second derivative is $-2 < 0$ , so it is a maximum: $x = 2$ , option C.

Report a problem with this question