Simplify
2x2-y2+2xy-(5x2-y2+4xy)
Consider 2x2-y2+2xy-(5x2-y2+4xy)
=2x2-y2+2xy-5x2+y2-4xy=(2x2-5x2)+(-y2+y2)+(2xy-4xy)=-3x2+(0)+(-2xy)=-3x2-2xy
Hence, 2x2-y2+2xy-(5x2-y2+4xy) is equal to -3x2-2xy