zad.5
a. 15ax-3ay+2ay-5ax-12ax+4xy-2=4xy-2-2ax-ay
b.-a2b2c2+abc-a2bc2+ab2c+a2b2c2+a2bc2-ab2c=abc
zad.6
A=3x-y B=-2x-5y
a.A-B=3x-y-(-2x-5y)=3x-y+2x+5y=5x+4y
b. -A-B=-(3x-y)-(-2x-5y)=-3x+y+2x+5y=6y-x
