X-Y=500 (1+15%)X-(1-10%)Y=950
10/x+y+3/x-y=-5 15/x+y-2/x-y=-1(用换元法解此方程组)
解方程组 X+Y=500 (1+15%)X-(1-10%)Y=950
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
方程组x-y=500① x+15%-(y-10%y)=950②
y=[x-1],
1.已知1/x+1/y=-1/x+y,则y/x+x/y=?
{3(x+y)+3(y+x)=1,3(x+y)+4(y-x)=-1
{4/(x+y)+6/(x-y)=3 {9/(x-y)-1/(x+y)=1
(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
若x-y=1,求代数式x(x-y)+y(y-x)+2013的值
已知4x=9y求(1)x+y/y (2)y-x/2x