664) (3aˇ2-2a)+(-aˇ2+3a)=3aˇ2-2a-aˇ2+3a=2aˇ2+a
(6cˇ2-2cd)+(10cˇ2+18cd)=6cˇ2-2cd+10cˇ2+18cd)=16cˇ2+16cd
(14mn-15m)+(-15mn-14m)=14mn-15m-15mn-14m=-mn-29m
(3aˇ2-7bˇ2)+(6bˇ2-2aˇ2)=aˇ2-bˇ2
665)(5xˇ3-3xˇ2-7)+(4+3xˇ2-5xˇ3)=-3
(zˇ2-3z+2)+(4z+8)+(3zˇ2-5)=4zˇ2+z+5
(3tˇ3-4tˇ2+7t)+(2tˇ3-6t+7)=5tˇ3-4tˇ2+t+7
(2aˇ2+5a)+(-aˇ2+a)+(aˇ2-3a-5)=2aˇ2+3a-5
666)(7x+y)-(-x-2y)=7x+y+x+2y=8x+3y
(b-3)-(2b+2)=b-3-2b-2=-b-5
(xˇ2-3x)-(2x+1)=xˇ2-3x-2x-1=xˇ2-5x-1
(5bˇ2+2b)-(4bˇ2-3b)=bˇ2+5b
667)(10a-2b+5c)-(-5a+20b-c)=15a-22b+6c
(16m-11n-7mn)-(6mn-10n+16m)=-n-13mn