I'm trying to factor -3x 3y-xy + y^2 I know that the first step is to pull out the negative which would leave -(3x-3y+xy-y^2) but I'm not sure where to go from there

One thing to notice is that there's a y^2 term, so a y must show up in both factors. Then note that there's a 3 in front of both an x and a y term, so that means the 3 must not be in the term that has both x and y.

At this point you know the factors must be of the form



Now play with the plus or minus signs to see what works. Post back if you're still having trouble.