To do this, you would need to use synthetic division.
-2 | 4 -3 10
-8 22
4 -11 32
Your reminder would be 32.
Sorry if my graph of synthetic division is a bit messy, you can only do so much on a phone!
Answer:
I can't solve and show it but only tell a method to do it!
So find the zero of the given factor:
i.e.

Now put its value (-1) in the polynomial

Now if the answer comes zero it is a factor.
You'll get your answer!
Answer:
if you meant x times y...
15 x 20 is 300.
if you meant x + y...
15 + 20 is 35.
if you meant anything else, please let me know
the way it was written confused me but I tried.