解析 (1)4x2y-(6xy-12xy+6-x2y)+1 =4x2y-6xy+12xy-6+x2y+1 =5x2y+6xy-5, 当x=2,y=-时,原式=5×22×(-)+6×2×(-)-5=-10-6-5=-21.
(2)原式=3a2b-(2ab2-6ab+3a2b+4ab)-2ab =3a2b-2ab2+6ab-3a2b-4ab-2ab =-2ab2, ∵(a+2)2+(3b-3)2=0, ∴a+2=0,且3b-3=0, ∴a=-2,且b=l, 当a=-2,b=1时,原式=-2×(-2)×12=4. |