SOLUTION: Graph (x+3) (x-2)^2=0 (use maxs, mins, x and y intercepts)

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Question 134056: Graph (x+3) (x-2)^2=0 (use maxs, mins, x and y intercepts)
Answer by solver91311(24713) About Me  (Show Source):
You can put this solution on YOUR website!
%28x%2B3%29+%28x-2%29%5E2=0 doesn't actually have a graph other than the three values (-3, 2, and 2) on the number line that satisfy the equation. You can, however, graph f%28x%29=%28x%2B3%29%28x-2%29%5E2, and I suspect that is what you really meant. (I sincerely hope your instructor didn't pose the question that way. If s/he did, go get your money back)

Zeros, or x-intercepts at -3, 2, and 2 (we should have an extrema at 2)

Expand:
f%28x%29=x%5E3-x%5E2-8x%2B12

Extreme points where f'(x) = 0, so:

f'(x) = 3x%5E2-2x-8. Set the first derivative equal to zero:

3x%5E2-2x-8=0
%283x%2B4%29%28x-2%29=0, hence critical points are at (-4%2F3,f%28-4%2F3%29) and (2,f%282%29).

We know that f%282%29=0, so we have a critical point at (2,0).

f%28-4%2F3%29=%28%28-4%2F3%29%2B3%29%28%28-4%2F3%29-2%29%5E2
f%28-4%2F3%29=%285%2F3%29%28-10%2F3%29%5E2
f%28-4%2F3%29=%285%2F3%29%28100%2F9%29
f%28-4%2F3%29=%28500%2F27%29

And we have an extreme point at -4%2F3,500%2F27)

f"(x)=6x-2
f"(2)=8-2=6%3E0 => (2,f(2)) is a local minimum
f"(-4/3)=6%28-4%2F3%29-2=-8-2=-10%3C0 => (-4%2F3,f%28-4%2F3%29) is a local maximum

The y-intercept is found by evaluating f(0):
f%280%29=0%5E3-0%5E2-80%2B12=12 hence the y-intercept is (0,12)


Using this information, we can make a rough sketch of the graph: