can I use u-substitution for int[2/(x^2+4x+5]dx ?

[cheffy]

integral of 2/(x^2+4x+5) dx

Please help! Thanks!

 

[Unco]

Re: u substitution(?)

integral of 2/(x^2+4x+5) dx

Completing the square in the denominator would be a good start. Can you see what this might lead to?

 

[mark]

u substition is not going to work you either have to use trig subsitition or partial fractions

just complete the square in the demonator

x^2 + 4x + 5 = x^2 +4x + 4 +5 -4 = (x+2)^2 +1

which equals

intergral 2/((x+2)^2+1)

which then can be solved using trig subsition

 

[cheffy]

I did what you said and I see how I should get my answer, but how do I get rid of the 5 in the denominator?

 

[mark]

that was a typo is was supposed to be 1

 

[cheffy]

Thank you so much! =D