let's recall the vertical line test, if a vertical line hits the graph or points twice, then is NOT a function. Check the picture below.
I hope it helps you get it right
Mouses steal cheese.Or idk
Answer: -4
Step-by-step:
-x^2+5x-1 x _ = 4x^2-20x+4
4x^2-20x+4 / -x^2+5x-1
In the blank the answer would be -4 which is the monomial.