20/x+10/y=7,28/x-25/y=2,x=?,y=?
[x(x-y)-y(x-y)+(x+y)(x-y)]÷2x其中x=2012 y=2013
解方程组(x+y)(x-2y)=-5 (x-y)(x+2y)=7
x+y/2+x-y/3=6,4(x+y)-3(x-y)=-20
{(x+y)/2+(x-y)/3=6 4(x+y)-3(x-y)=-20
4(x+y)-3(x-y)=-20,2/x+y+3/x-y=6
若(x-y)/(x+y)=3 则(x+2y)/(6x-7y)等于
已知2x-y=10,求[(x²+y²)-(x-y)²+2y(x-y)]/4y
已知X-Y/X+Y=3,求代数式2(x-y)/X+Y-3X+Y/X+Y
已知x-y/x+y=3,求代数式5(x-y)/x+y-x+y/2(x-y)
X+Y=7(100X+Y)-(10Y+X)=(10Y+X)-(10X+Y)
y'-2y=(e^x)-x
y'+2y/x=x通解