若x+2y=1,2x-3y=2,则2x+4y-6/2+6x-9y/4=?

若2/x-1/y=3,求[y/x-y/x-y(x-y/x-x+y)]/x-2y/x的值 若(x-y)/(x+y)=3 则(x+2y)/(6x-7y)等于 若2x=3y,则(x*x+y*y)/x*x=? x-y/x-x+y/y-(x+y)(x-y)/y² y/x=2 若x+y=4,则多项式1/2(x+y)+4(x-y)-3（x-y）-3/2(x+y)-x+y值是（） 若2x-3y+4=0则x（x*x-1)+x(5-x*x)-6y+7 若x,y满足|x-y+1|+(x+y+3)^2=0则x^2-y^2= 若x,y满足|2x-y-3|+|3x+2y+1|=0,则x= y= 若变量x,y满足约束条件{x>=-1;y>=x;3x+2y 若f(x+y,y/x)=x^2-y^2,则F(X,Y)= (3x-y)^2+(3x+y)(3x-y),x=1,y=-2 二元一次方程 ：2(x+y)-(x-y)=3 (x+y)-2(x-y)=1 若x*x+y*y=x+y-1/2,求x,y的值如题 2(x+y)-3(x-y)=1 6(x+y)+(x-y)=51 {3(x+y)-4(x-y)=4 {x+y/2 + x-y/6=1 变量x,y满足约束条件,x+y>=3,x-y>=-1,2x-y (x-y)^2+(x+y)(x-y) 其中 X =3 Y=-1 (x-y)/(x+y)=3求( 3x-2y-1)/(x+y-5)