5/2x+9/y=2 ; 15/x-12/y=1
先化简再求值(x-y)(x+y)-(x-2y) 的完全平方+x(3x-5y)-(x-y)(x-2y),其中x=1/2 y
已知X.x+y.y-4x+2y+5=0,求4X.X-12X Y+9Y.y的值
已知4x=9y求(1)x+y/y (2)y-x/2x
x+y=3 x+2y=9 3/x+1=y y-x=3 y=2x-3 y-3x=1 2(x+1)-y=6 7x-5y=-9
10/x+y+3/x-y=-5 15/x+y-2/x-y=-1(用换元法解此方程组)
已知x-y/x+y=3,求代数式5(x-y)/x+y-x+y/2(x-y)
化简[(3x+4y)^2-(2x+y)(2x-y)+(-x+y)(5x-y)]除以-2y,其中x=-1,y=1
已知x=1/3,y=-1/2,求代数式x-(x+y)+(x+2y)-(x+3y)+(x+4y)-(x+5y)+...-(
分式的加减:[(x/y-y/x)除以(x+y)+x(1/y-1/x)]除以1+x/y,其中x=5,y=2
已知x²+y²+5=2x+4y,求【2x²-(x-y)(x-y)】【(x+y-1)(x-y
先化简,再求值[(2x+y)^2-(2x+y)(2x-y)-y(5x+y)]÷(1/2y),其中x-y=2
解方程组: {3x+2y=13 3x-2y=5 {x-y/3=x+y/2+1 2x-5y=9