Hi I need help on an improper integral.

The integral from negative infinity to 3, where f(x)= 1/(x^2+9)

I know I need to get it to the format, x^2+1 on the bottom, in order to get it to a tangent inverse; however, I am having trouble with my algebra to get to this point. Moreover we cannot use u-sub, because y' of x^2+9= 2x, and we cannot make an X; so this is our only option.