Friday

October 31, 2014

October 31, 2014

Posted by **W** on Monday, November 21, 2011 at 12:12am.

Thanks for your help!

- Calculus -
**Steve**, Monday, November 21, 2011 at 4:46amI think you may be going about things backwards. If

u = 3/x

du = -3/x^2 dx

and your integrand becomes e^u du/(-3) = -1/3 Int(e^u du) = -1/3 e^u = -1/3 e^3/x

check: taking the derivative of -1/3 e^3/x we get

-1/3 * e^3/x * -3/x^2 = e^(3/x) / x^2

So, evaluating at 3 and 1,

-1/3 e^(3/3) + 1/3 e^(3/1) = 1/3 (e^3 - e)

**Answer this Question**

**Related Questions**

calculus-integration! - should i use substitution?? if yes how should should i ...

Integrating Factors - I've been working on this hw problem for a while now, but ...

Integral calculus - Please do help solve the followings 1) Integrate e^4 dx 2) ...

calculus - integrate 3/25+4x^3....use 2x=5tanΦ as a substitution

calculus - How would you integrate tan5xdx ? Thanks in advance. Can you use u ...

Calculus - How to integrate dx/(4-5 sin x) using t-substitution method(i.e. ...

Calculus - Can someone help me to integrate by substitution the indefinite ...

Calculus II - How do you integrate the function -- > sinx (4^cosx) from 0 to ...

calculus - integrate x*(x+1)^9dx I believe the substitution method is the proper...

calculus - Integrate x/(x^2 + 4) dx via trig substitution and by u=x^2+4 ...