Define f:[-4,0]->R by f(x)=2 -18/x+3 for x -3 and f(-3)= -12. Show that f is continuous at -3.

At first I was going to try to show that the lim_(x->-3)= -12 and I was going to reduce and stuff but im getting lost because its not working out smoothly. Also, can I just go ahead and show that (with help) or do I have to show a proof of it?