654
а) (3а²-2а)+(-а²+3а)=
=3а²-2а-а²+3а=2а²+а
б) (6c²-2cd)+(10c²+18cd)=
=6c²-2cd+10c²+18cd=
=16c²+16cd
655
a) (5x³-3x²-7)+(4+3x²-5x³)=
=5x³-3x²-7+4+3x²-5x³=
= -3
б) (z²-3z+2)+(4z+8)+(3z²-5)=
=z²-3z+2+4z+8+3z²-5=
=4z²+z+5
656
a)(7x+y)-(-x-2y)=
=7x+y+x+2y=8x+3y
б) (b-3)-(2b+2)=
= b-3-2b-2= -b-5