SOLUTION: If f'(x) = 9 x+ 12 and f(5) = -11, find f(x). If f'(x) = 9 x+ 12 I have f(x) = (9/2)x^2 + 12x + C But I am not sure where to go from there I am completely lost.. THAN

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Question 994562: If f'(x) = 9 x+ 12 and f(5) = -11, find f(x).
If f'(x) = 9 x+ 12
I have f(x) = (9/2)x^2 + 12x + C
But I am not sure where to go from there
I am completely lost..
THANK YOU
Found 2 solutions by stanbon, solver91311:
Answer by stanbon(75887) (Show Source):
You can put this solution on YOUR website!
If f ′(x) = 9 x+ 12 and f(5) = −11, find f(x).
If f ′(x) = 9 x+ 12
I have f (x) = 9x^2/2 + 12x + C
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Solve for "C" using f(5) = -11
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-11 = (9/2)(5)^2+12(5) + C
-71 = (9*25/2 +C
-71 = 112.5
C = -183.5
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f(x) = (9/2)^2 + 12x - 183.5
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Cheers,
Stan H.
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Answer by solver91311(24713) (Show Source):
You can put this solution on YOUR website!

I did a little editing on your post for readability's sake but did not change the meaning in any way.

You certainly aren't completely lost since everything you posted was correct. I'm only going to give you a hint at this point. Since you integrated the derivative, the result was the family of functions that have that derivative. So what does the fact that tell you when you know that ?

John

My calculator said it, I believe it, that settles it