1/2x+1/3y=16 1/2x+1/4y=14 求得数）打错了，题目是2分之1x+3分之1y=16 2分之1y+4分之1=14

若2/x-1/y=3,求[y/x-y/x-y(x-y/x-x+y)]/x-2y/x的值 (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 (x-y)/(x+y)=3求( 3x-2y-1)/(x+y-5) 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 函数,y=3x/(x^2+x+1) ,x 函数y=3x/(x^2+x+1) （x x+y+2(-x-y+1)=3(1-y-x)-4-(y+x-1),x+y=? {(x+y)/2+(x-y)/3=1,(x+y)-5(x-y)=2.求x=?,y=? x²/xy-x/y 3x/4x+y - x-2y/4x+y (1-y/y+x)÷x/y²-x² 化简 3x(x^2-x-1)-(x+1)(3x^-x) X^3(x-y)+x(y-x) 2(x-y)/3-(x+y)/4=-1 (1) 6(x+y)-4(2x-y)=16 (2) [3x^2-(x+y)(y-x)][2(-x-y)(y-x)+2x^2+3y^2],其中x=-2分之1,y=1.5 (2x-2y)/3-(x-y)=-1和6(x+y)-4(2x-y)=16 3分之2(X-Y)-4分之X+Y=-1,3(X+Y)-2(X-Y)=16