I have the following integral

$\displaystyle \int\frac{4x+7}{x^2+6x+14}$

Now I know there is a "trick" to finding part of the denominator as long as the roots are negative. You just take 1/2 of B^2.

So in this example it would be $\displaystyle (x+3)^2$. But I also know that you need to tack a +5 to the end. How was this +5 found, is there some kind of trick?