｛5x+2y=18,y=－x
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｛5x+2y=18,y=－x｛5x+2y=18,y=－x｛5x+2y=18,y=－xx=6y=-6把2式代入1式得5x+2（-x）=183x=18x=6把x=6代入2式y=-6求,给个最佳咯.x=6y
｛5x+2y=18,y=－x
｛5x+2y=18,y=－x
｛5x+2y=18,y=－x
x=6 y=-6
把2式代入1式 得 5x+2（-x）=18
3x=18
x=6
把 x=6 代入2式 y=-6
求,给个最佳咯.
x=6 y=-6
X=6
x=6 y=-6
5x-2x=18
3x=18
x=6
y=-6
用-x代替y，得5X-2X=18解出就可以了
x＝6 y＝–6
根据已给条件，将y=-x带入方程式中，得出
5x-2x=18,即3x=18, x=6, y=-x=-6
x=6 y=-6
x=6，y=—6
x-y/x-x+y/y-(x+y)(x-y)/y² y/x=2
｛5x+2y=18,y=－x
已知x-y/x+y=3,求代数式5(x-y)/x+y-x+y/2(x-y)
2(x-y)=5y,x-y=-5
x-y / 5y= (y-x)^2 / ( )
x*x+2x+y*y-4y+5=0 x= y=
x+y/2+x-y/6=5 2(x+y)-3(x-y)=-2
解方程组(x+y)(x-2y)=-5 (x-y)(x+2y)=7
3(x+y)+2(x-y)=36 4(x+y)-5(x-y)=2
4(x-y)-3(x-y)=9 5(x-y)+2(x-y)=11
3(x+y)-4(x-y)=11,2(x-y)+5(x+y)=27
{6(x-y)-7(x+y)=21 {2(x-y)-5(x+y)=-1
6(x-y)-2(x+y)=14 3(x-y)+(x+y)=5
求(X+Y)(X-Y)(X²+Y²),X=5 Y=2,
(x-y)/(x+y)=3求( 3x-2y-1)/(x+y-5)
先化简再求值(x-y)(x-2y)+(x-2y)(x-3y)-2(x-3y)(x-4y) x=4 y=5
解方程组：2/(x+y)+5/(x-y)=18 9/(x+y)-10/(y-x)=66
解方程组:2/(x+y)+5/(x-y)=18 9/(x+y)-10/(y-x)=66