求1/2x-2/3y=-15/2,1/2y-5/3y=-4/3分别求出x,y的值

(x-y)/(x+y)=3求( 3x-2y-1)/(x+y-5) 若2/x-1/y=3,求[y/x-y/x-y(x-y/x-x+y)]/x-2y/x的值 {(x+y)/2+(x-y)/3=1,(x+y)-5(x-y)=2.求x=?,y=? 已知：2x+y=6,x-3y=1 求7y(x-3y)(x-3y)-2(3y-x)(3y-x) 已知x-y=1,求[(x+2y)^2+(2x+y)(x-4y)-3(x+y)(x-y)]除以y的值大神们帮帮忙 x*y=6x-y=1求X Y是多少?X=3 Y=2 求公式! 已知x-y=1,求[(x+2y)²+(2x+y)(x-4y)-3(x+y)(x-y)]÷y的值 求导数y=3x-x^2 求y',y'/ x=1 y'/x=0 x+2y=2x+y+1=7x-y 求：2x-y? 若x*x+y*y=x+y-1/2,求x,y的值如题 1奥数题x-2y/x+2y=3,求x-2y/3(x+2y)-3(x-2y)/x-2y的差 2分之x+2y=3分之2x-y=1求x，y 2y=x-3 y+2=2x-1 求x y 1/x-1/y=3,求2x+3xy-2y/x-y 2x+4y=3 -3x-2y=1 ..求x和y 2x+y=3,3x+2y=1【求X.Y】 已知x+y=a,2x-y=-2a,求[（x/y-y/x)/(x+y)-x(1/x-1/y)]/[(x+1)/y]的值 x-2y=15,xy=-25,求x*x+4y*y-1