How do I factorize this numerator? $$\lim_{x\to -3}   \frac 1{x+3} + \frac 4{x^2+2x-3}$$
I have the solution I just need to know how i turn that into:
$$\frac {(x-1)+4}{(x+3)(x-1)}$$
I know this might be really simple but I'm not sure how to factorise the numerator.
Thanks in advance!

First off note that $$x^2 + 2x -3  = (x+3)(x-1)$$ We can therefore rewrite your equation as $$\lim_{x \to -3} \frac 1{x+3} + \frac 4{(x+3)(x-1)} \\ \lim_{x \to -3} \frac {(x-1)}{(x+3)(x-1)} + \frac 4{(x+3)(x-1)} \\ \lim_{x \to -3} \frac {x-1 + 4}{(x+3)(x-1)} \\ \lim_{x \to -3} \frac {x+3}{(x+3)(x-1)} \\ \lim_{x \to -3} \frac {1}{x-1} \\ -\frac{1}{4}$$
