SOLUTION: Please help!!! Find the critical values,points of inflection and discuss the concavity of the graph of f(x)=(x-1)^3(x+3) and then sketch a neat graph of f,showing all the sal

Algebra ->  Finance -> SOLUTION: Please help!!! Find the critical values,points of inflection and discuss the concavity of the graph of f(x)=(x-1)^3(x+3) and then sketch a neat graph of f,showing all the sal      Log On


   



Question 1093170: Please help!!!
Find the critical values,points of inflection and discuss the concavity of the graph of
f(x)=(x-1)^3(x+3)
and then sketch a neat graph of f,showing all the salient points.

Answer by Boreal(15235) About Me  (Show Source):
You can put this solution on YOUR website!
f(x)=(x-1)^3(x+3)
f'(x)=(x-1)^3+3(x-1)^2(x+3)=x^3-3x^2+3x-1+3(x^3+x^2-5x+3)=4x^3-12x+8
that is 4(x^3-3x+2)=4(x+2)(x^2-2x+1)
Set equal to 0, and critical points are at x=-2 y=-27 and x=1 y=0
second derivative is 4(3x^2-3)=4(x^2-1), so inflection points are where x=1 and -1, because the second derivative is 0.
Where x=-2, y is positive so a minimum.
graph%28300%2C300%2C-5%2C5%2C-35%2C30%2C%28x-1%29%5E3%28x%2B3%29%29
first derivative graph
graph%28300%2C300%2C-5%2C5%2C-25%2C30%2C4%28x%2B2%29%28x%5E2-2x%2B1%29%29