$解:②-①得2x=2,解得x=1,$ $把x=1代入①得1+2y=1,解得y=0,$ $所以\left\{\begin{array}{l}x=1 \\ y=0\end{array}\right. $ $解:②+①得4y=4,解得y=1$ $将y=1代入②得x=1,$ $所以\left\{\begin{array}{l}x=1 \\ y=1\end{array}\right.$ $解:由① -②×2:y=-2，$ $把y=—2代入①得：4x-6=6，$ $解得：x=3，$ $则方程组的解为\left\{\begin{array}{l}x=3, \\ y=-2\end{array}\right. $ $解:由①得：x=-1-3y③，$ $把③代入②得：3(-1-3y)-2y=8，$ $解得：y=-1，把y=-1代入③$ $得x=-1-3×(-1)=2，$ $所以\left\{\begin{array}{l}x=2, \\ y=-1\end{array}\right. $ $解:① \times 3-② \times 2 , 得 -5 y=1 ,$ $解得: y=-\frac{1}{5} ,$ $将其代入①式, 得 2 x+\frac{3}{5}=5 ,$ $解得: x=\frac{11}{5} ,$ $故方程组的解为: \left\{\begin{array}{l}x=\frac{11}{5} \\ y=-\frac{1}{5}\end{array}\right. $ $解:方程①×（-5）得：-10x-25y=50 ③$ $方程②×2得：10x-6y=12 ④$ $③+④得，-31y=62，解得，y=-2.$ $将y=-2代入①，得x=0.$ $所以\left\{\begin{array}{l}x=0, \\ y=-2\end{array}\right. $
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