(5a+4c+7b)+(5c-3b-6a) (8xy-x*+y*)-(x*-y*+8xy)
=5a+4c+7b+5c-3b-6a =8xy-x*+y*-x*+y*-8xy
=-a+4b+9c =-2x*+2y*
=a-4b-9c =2x*-2y*
(2x*-1/2+3x)-4(x-x*+1/2) =2(x*-y*)
=2x*-1/2+3x-4x+4x*-2
=6x*-x-3/2
3x*-[7x-(4x-3)-2x*]
=3x*-(7x-4x+3-2x*)
=3x*-7x+4x-3+2x*
=5x*-3x-3