18x-9y=-9 5x-9y=-35

4(x-y)-3(x-y)=9 5(x-y)+2(x-y)=11 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 5x=3y,(2x+y)的平方=5x(x+y)+9 3x-2y=9 x-3y=2 x+y=5 x+2y=3 y=x 2x+y=8 已知X.x+y.y-4x+2y+5=0,求4X.X-12X Y+9Y.y的值 y+10x=x+y+9 10y+x=y+10x+27 3(x+y)-2(x-y)=11 4(x+y)+3(x-y)=9 f(x,y)=x*x*x+y*y*y-9xy+27极值 18x/34y=9/1 x/y=?/? 计算18x+9y=14x+15y 5x-y=110 9y-x=110 Y=x+3 7x+5y=9 y-x=3 7x+5y=-9 y=x+3 7x+5y=9 x y=5 x-y=9怎么解 x+y=5 x-y=9怎么解 {y=x+3,7x+5y+9;