f(x)=10/x

F(x)=???

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- Nov 29th 2008, 03:41 AMNo Logic Senseintegration
f(x)=10/x

F(x)=??? - Nov 29th 2008, 04:02 AMKrizalid
Pull back the constant and remember what the derivative of natural log. is.

- Nov 29th 2008, 04:04 AMNo Logic Sense
my book says:

f(x)=1/x ---> F(x)=ln(x)

But I don't see what happens to 1 and 10 in my case - Nov 29th 2008, 04:19 AMKrizalid
As I said, you can just pull out that constant, it's a property. It says $\displaystyle \int k\cdot f(x)\,dx=k\int f(x)\,dx.$

- Nov 29th 2008, 04:38 AMNo Logic Sense
Oh, so my answer is just

F(x)=ln(x)+k

??? - Nov 29th 2008, 05:11 AMrunning-gag
No

If F(x)=ln(x)+k then f(x)=1/x

Answer is simply F(x)=10 lnx + k