x+y=28 12x:18y=1:2
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
(3x-y)^2+(3x+y)(3x-y),x=1,y=-2
{3(x+y)-4(x-y)=4 {x+y/2 + x-y/6=1
已知4x=9y求(1)x+y/y (2)y-x/2x
4/X+1/Y=2,XY=-1,求代数式4Y-X/X-2Y/(x+2y-12Y²/x-2y)的值
解方程组:(x+3)(y-2)=(x-3)(y+10),(x+1)(y+3)=(x-2)(y+12)
y=(x^2+x)/(x+1)
y/3-x+1/6=3 2(x-y/2)=3(x+y/18)
2(x+y) 3x+3y=24 x+y/2x x y/2y= 1
设x>1,y>0,若x^y+x^-y=2根号2,则x^y-x^-y等于
[x(x-y)-y(x-y)+(x+y)(x-y)]÷2x其中x=2012 y=2013
化简[(3x+4y)^2-(2x+y)(2x-y)+(-x+y)(5x-y)]除以-2y,其中x=-1,y=1