1-The function f(x)=2x+9x^−1 has one relative minimum and one
relative maximum.

2-Find the two critical points and determine if the function is
increasing or decreasing on the given intervals.
y=6x^4+4x^3

3- Consider the function f(x)=12×5+75×4−120×3+7. For this
function there are four important intervals:(−∞,A], [A,B],[B,C],
and [C,∞) whereA, B, and C are the critical numbers. Find A,B,C and
determine wether they are max or min or niether