{x-y=2,4(x-y)-y=5 {4x-3y=11,2x+y=13

x*x+2x+y*y-4y+5=0 x= y= 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 先化简再求值(x-y)(x-2y)+(x-2y)(x-3y)-2(x-3y)(x-4y) x=4 y=5 若(x*x+y*y)(x*x+y*y)-4x*x*y*y=0,求代数式(x*x+5xy+y*y)/(x*x+2xy+y*y)的值 已知x*x+4x+y*y-2y+5=0,则x*x+y*y=? (x-y) (x-2y)+(x+2y) (x-3y)-2(x-3y) (x-4y)= 化简[(3x+4y)^2-(2x+y)(2x-y)+(-x+y)(5x-y)]除以-2y,其中x=-1,y=1 5x-4y(y-x)=? (x-4y)(2x+y)= (4x-2y-z)-{5x[8y-2y-(x+y)]-x+(3y-10z)]=? kuaihuajian 化简求值：2(x+y)(x-2y)-2x(x+y),其中x、y满足x^2+y^2-2x+4y=-5 x-y/x-x+y/y-(x+y)(x-y)/y² y/x=2 x+y／y=5／4,则x／y=---------------- 已知：4x = 5y,求(x+y) ：y y'=（y/x）^2+y/x+4微分方程 4x方y/(x-2y)(x+2y)怎么算[x方/x-2y]-4x方y/(x-2y)(x+2y)=?