初二方程组一道————————————————————在线等x²+2xy+y²=1 { 2x²-y=2 解方程组
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初二方程组一道————————————————————在线等x²+2xy+y²=1 { 2x²-y=2 解方程组
初二方程组一道————————————————————在线等
x²+2xy+y²=1
{
2x²-y=2
解方程组
初二方程组一道————————————————————在线等x²+2xy+y²=1 { 2x²-y=2 解方程组
x²+2xy+y²=1
(x+y)^2=1
x+y=1或-1
x+y=1,y=1-x,
2x²-y=2
2x²-1+x=2
(2x+3)(x-1)=0
x=-3/2或1
y=5/2或0
x+y=-1,y=-1-x,
2x²-y=2
2x²+1+x=2
(2x-1)(x+1)=0
x=1/2或-1
y=-1/2或0
x²+2xy+y²=1 (x+y)^2=1 x+y=1或x+y=-1
2x²-y=2 2x^2-y=2
1. x+y=1
2x^2-y=2 相加 2x^2+x-1=0 x=-1或x=1/2
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x²+2xy+y²=1 (x+y)^2=1 x+y=1或x+y=-1
2x²-y=2 2x^2-y=2
1. x+y=1
2x^2-y=2 相加 2x^2+x-1=0 x=-1或x=1/2
x=-1 y=0
x=1/2 y=-3/2
2. x+y=-1
2x^2-y=2 相加 2x^2+x+1=0 无解
所以
x=-1 y=0 或 x=1/2 y=-3/2
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