(1)6xy-3[3y2-(x2-2xy)+1], =6xy-3[3y2-x2+2xy+1], =6xy-9y2+3x2-6xy-3, =3x2-9y2-3;
(2)-14÷(-5)2×(-)+|0.8-1|, =-1÷25×(-)+|0.8-1|, =+0.2, =;
(3)等式左边=x-2(x-3x+3)=x-2x+6x-6=5x-6, ∴方程可化为5x-6=8, 移项并合并,得 5x=14, 系数化为1得 x=2.8;
(4)去分母,得 2(x+1)-(x-2)=3(4-x)+6, 去括号得: 2x+2-x+2=12-3x+6, 移项,得 2x-x+3x=12+6-2-2, 合并同类项,得 4x=14, 系数化为1,得 x=3.5. |