a)(x²-2xy+yz):(x-y)
=(x²:x-y)+(-2xy:x-y)+(yz:x-y)
=x-y-2+zx
b)(x³+y³):(x+y)
=(x³:x+y)+(y³:x+y)
=x²+y+x+y²
c)(2x^4-5x³+2x²-2x-1):(x²-x-1)
=(2x^4:x²-x-1)+(-5x³:x²-x-1)+(2x²:x²-x-1)+(-2x:x²-x-1)+(-1:x²-x-1)
=2x²-2x³-2x^4-5x+5x²+5x³+2-2x-2x²-2+2+2x-1x²+1x+1
=3x³-2x^4-4x+4x²+3