1、3ab-4ab+8ab-7ab+ab=______． a=3,b=22．7x-(5x-5y)-y=______． x=2,y=33．23a3bc2-15ab2c+8abc-24a3bc2-8abc=______． a=2,b=1,c=34．-7x2+6x+13x2-4x-5x2=______． x=25．2y+(-2y+5)-(3y+2)＝______． y=-16．(...