SOLUTION: Given f(x) = –x3 – 3x2 – 2x – 6, find f(–3), f(0), and f(3) Now do I have to substitue a number for x? I am so confused!! Thanks for your help!

Algebra ->  Functions -> SOLUTION: Given f(x) = –x3 – 3x2 – 2x – 6, find f(–3), f(0), and f(3) Now do I have to substitue a number for x? I am so confused!! Thanks for your help!      Log On


   

Question 75652: Given f(x) = –x3 – 3x2 – 2x – 6, find f(–3), f(0), and f(3)
Now do I have to substitue a number for x? I am so confused!! Thanks for your help!
Found 2 solutions by jim_thompson5910, checkley75:
Answer by jim_thompson5910(35256) About Me  (Show Source):
You can put this solution on YOUR website!
When you say f(x)= some polynomial it will be in x form. When you say f(0), you are replacing every x you have with 0. So for f(-3) it will look like:
f%28x%29+=+-x%5E3+-3x%5E2-+2x-+6
f%28-3%29+=+-%28-3%29%5E3+-3%28-3%29%5E2-+2%28-3%29-+6
f%28-3%29+=+-%28-27%29+-3%289%29-+2%28-3%29-+6
f%28-3%29+=+27+-27+%2B+6-+6
f%28-3%29+=+0



f(0) will look like:
f%280%29+=+-%280%29%5E3+-3%280%29%5E2-+2%280%29-+6
f%280%29+=+0-0-+0-+6
f%280%29+=-+6



and f(3) looks like:
f%283%29+=+-%283%29%5E3+-3%283%29%5E2-+2%283%29-+6
f%283%29+=+-%2827%29+-3%289%29-+2%283%29-+6
f%283%29+=+-27+-27+-+6-+6
f%283%29+=+-66
If you graphed this function you will see this points visually.
+graph%28+300%2C+200%2C+-6%2C+5%2C+-10%2C+10%2C+-x%5E3+-3x%5E2-+2x-+6%29+ Here's the graph of y=-x%5E3+-3x%5E2-+2x-+6 where you can see (-3,0) and (0,-6) and (3,-66) is somewhere way off the page.

Answer by checkley75(3666) About Me  (Show Source):
You can put this solution on YOUR website!
F(X)=-X^3-3X^2-2X-6 NOW WE REPLACES ALL Xs WITH (-3) AND SOLVE
F(-3)=-(-3)^3-3(-3)^2-2(-3)-6
F(-3)=-(-27)-3(9)+6-6
F(-3)=27-27
F(-3)=0
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F(0)=-(0)^3-3(0)^2-2*0-6
F(0)=0-0-0-6
F(0)=-6
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F(3)=-(3)^3-3(3)^2-2*3-6
F(3)=-27-27-6-6
F(3)=-66
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