Question

The function f(x) = -x2 + 4x + 9 assumes its maximum value for which value of x?

Answer 1

so... what are we looking for?

Answer 2

Take the first derivative, set it equal to 0, solve for x. Then check whether it's a max or a min.

Answer 3

No need for derivative, just try to wl

Answer 4

Rewrite the equation into standard form of a parabola by completing the square

Answer 5

oh just find the vertex

Answer 6

Find the vertex (h.,k) K is your maximum and the value you are looking for is h