Question

Consider the function f(x)=2x+9x^–1.?
For this function there are four important intervals: (-inf,–A], [A,B),(B,C), and [C,inf)

where A, and C are the critical numbers and the function is not defined at B.

Find A= ?????
and B= 0
and C =?????

Answer 1

i have this one already

Answer 2

In that case I will assume that you no longer need help.

Since f(x) = 2x + 9/x
f'(x) = 2 - 9/x^2
The function has extreme values at
x = 3/sqrt2 and = -3/sqrt2
Those are the points A and C.