｛5x+2y=18,

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｛5x+2y=18,｛5x+2y=18,｛5x+2y=18,将y=-x带入5x+2y=185x+2(-y)=183x=18x=6y=-6自己想为什么我就没看懂是啥呢？》1y=－x带入5x+2y=18,

｛5x+2y=18,
｛5x+2y=18,

｛5x+2y=18,
将y=-x 带入 5x+2y=18
5x+2(-y)=18
3x=18
x=6
y=-6

自己想

为什么我就没看懂是啥呢？》

y=－x带入5x+2y=18,
即5x-2x=18
3x=18
x=6
带入y=－x得，y=-6

求二元一次方程:2代入1中得x=6,再将练6入2中得y=-6

Y=-X
5X-2X=18
3X=18
X=6 Y=-6

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