Over the x-value interval [−10,10][10,10], what are the absolute extrema of f(x)=x^2f(x)=x2?

1 Answer
Jul 27, 2015

The absolute maximum value is 100 at x=\pm 10x=±10 and the absolute minimum value is 0 at x=0x=0.

Explanation:

This is clear just by knowing the graph of y=f(x)=x^2y=f(x)=x2 as an upward-opening parabola with a vertex at the point (0,0)(0,0).

You can also use calculus (just a little preview if you are in precalculus). Since the derivative f'(x)=2x, the only critical point of the function is x=0. Now you compare the value of the continuous function f at the critical point and the endpoints x=\pm 10 of the closed and bounded interval [-10,10]:

f(0)=0^2=0, f(\pm 10)=10^2=100.

This guarantees that the absolute maximum value is 100 at x=\pm 10 and the absolute minimum value is 0 at x=0.