Wednesday, 28 May 2014

`int x/(x^2-6x+10)^2 dx` Use integration tables to find the indefinite integral.

`intx/(x^2-6x+10)^2dx`


Let's rewrite the integrand as,


`=1/2int(2x)/(x^2-6x+10)^2dx`


`=1/2int(2x-6+6)/(x^2-6x+10)^2dx`


`=1/2[int(2x-6)/(x^2-6x+10)^2dx+int6/(x^2-6x+10)^2dx]`  --------------------(1)


Now let' evaluate each of the above two integrals separately,


`int(2x-6)/(x^2-6x+10)^2dx`


Let's apply integral substitution:`u=x^2-6x+10`


`=>du=(2x-6)dx`


`=int1/u^2du`


`=intu^(-2)du`


Now from the integer tables:`intu^ndu=u^(n+1)/(n+1)+C`


`=u^(-2+1)/(-2+1)`


`=-1/u`


Substitute back `u=x^2-6x+10`


`=-1/(x^2-6x+10)`                    -----------------------------(2)


Now let's evaluate the second integral,


`int6/(x^2-6x+10)^2dx`


Take the constant out,


`=6int1/(x^2-6x+10)^2dx`


Complete the square of the term in the denominator.


`=6int1/((x-3)^2+1)^2dx`  


Let's apply integral substitution:`u=x-3`


...

`intx/(x^2-6x+10)^2dx`


Let's rewrite the integrand as,


`=1/2int(2x)/(x^2-6x+10)^2dx`


`=1/2int(2x-6+6)/(x^2-6x+10)^2dx`


`=1/2[int(2x-6)/(x^2-6x+10)^2dx+int6/(x^2-6x+10)^2dx]`  --------------------(1)


Now let' evaluate each of the above two integrals separately,


`int(2x-6)/(x^2-6x+10)^2dx`


Let's apply integral substitution:`u=x^2-6x+10`


`=>du=(2x-6)dx`


`=int1/u^2du`


`=intu^(-2)du`


Now from the integer tables:`intu^ndu=u^(n+1)/(n+1)+C`


`=u^(-2+1)/(-2+1)`


`=-1/u`


Substitute back `u=x^2-6x+10`


`=-1/(x^2-6x+10)`                    -----------------------------(2)


Now let's evaluate the second integral,


`int6/(x^2-6x+10)^2dx`


Take the constant out,


`=6int1/(x^2-6x+10)^2dx`


Complete the square of the term in the denominator.


`=6int1/((x-3)^2+1)^2dx`  


Let's apply integral substitution:`u=x-3`


`=>du=dx`


`=6int1/(u^2+1^2)^2du`


Now use the following from the integration tables:


`int1/(a^2+-u^2)^ndu=1/(2a^2(n-1))[u/(a^2+-u^2)^(n-1)+(2n-3)int1/(a^2+-u^2)^(n-1)du]`


`=6{1/(2(1)^2(2-1))[u/(1^2+u^2)^(2-1)+(2(2)-3)int1/(1^2+u^2)^(2-1)du]}`


`=6{1/2[u/(1+u^2)+int1/(1^2+u^2)du]}`


Now from the integration table:`int1/(a^2+u^2)du=1/aarctan(u/a)+C`


`=6{1/2[u/(1+u^2)+arctan(u/1)]}`


`=(3u)/(1+u^2)+3arctan(u)`


Substitute back `u=x-3`


`=(3(x-3))/(1+(x-3)^2)+3arctan(x-3)`


`=(3x-9)/(1+x^2-6x+9)+3arctan(x-3)`


`=(3x-9)/(x^2-6x+10)+3arctan(x-3)`    -------------------------(3)


Plug back the results of the integrals 2 and 3 in 1


`int1/(x^2-6x+10)^2dx=1/2[-1/(x^2-6x+10)+(3x-9)/(x^2-6x+10)+3arctan(x-3)]`


`=1/2[(3x-9-1)/(x^2-6x+10)+3arctan(x-3)]`


`=1/2[(3x-10)/(x^2-6x+10)+3arctan(x-3)]`


`=(3x-10)/(2(x^2-6x+10))+3/2arctan(x-3)`


Add a constant C to the solution,


`=(3x-10)/(2(x^2-6x+10))+3/2arctan(x-3)+C`


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