f(x)=x^2cos(3x) is f increasing or decreasing at x=4. determine the type of concavity at x=4

Question

Please HELP

Answer 1

Why don't you work on this, based on what you know.

You need f' and for that you'll need to use the product rule, the power rule and the chain rule.

 

You'll need to find critical points by setting f' = 0.

 

For concavity, you'll need the second derivative f" and you'll have to evaluate f"(4); if"(4) > 0, concave upward; if f"(4)<0, downward.

 

Give this an honest effort, and tell us what you got for derivatives, and let us critique your work and conclusions.