{3x-y-3=0 {4x+y=17
设x,y满足约束条件x>=0 y>=x 4x+3y
已知x,y满足x²+y²-4x+6y+13=0则(3x+y)²-(3x+y)(3x-y)的
已知3x^2+xy-2y^2=0,求{(x+y)/(x-y)+4xy/(y^2-x^2)}/{(x+3y)*(x-y)}
{3(x+y)+3(y+x)=1,3(x+y)+4(y-x)=-1
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
{3(x+y)-4(x-y)=4 {x+y/2 + x-y/6=1
(5x+3y)(3y-5x)-(4x-y)(4y+x)=
3(x+y)-4(x-y)=11,2(x-y)+5(x+y)=27
{4/(x+y)+6/(x-y)=3 {9/(x-y)-1/(x+y)=1
已知|3x-y|+|x+y|=0,求x-y除以x*y的值.