Y=X-1/2-3X=-2x-1/2.请告诉我-2x-1/2如何算出来的.

x-y/x+y=-1/2,x*x-xy-2y*y/x*x-3xy+2y*y的解是多少?同上,请将过程写出, {(x+y)/2+(x-y)/3=1,(x+y)-5(x-y)=2.求x=?,y=? 函数,y=3x/(x^2+x+1) ,x 函数y=3x/(x^2+x+1) （x 若2/x-1/y=3,求[y/x-y/x-y(x-y/x-x+y)]/x-2y/x的值 一个“整式的乘法”的问题请先阅读下列解题过程,再仿做下面的问题.已知X*X + X - 1=0,求X*X*X + 2*X*X + 3的值.解X*X*X + 2X*X +3=X*X*X +X*X -X +X*X +X +3=X{X*X +X -1} +X*X +X -1 +4=0+0+4=4+ x + X*X + X*X*X=0.+ X*X + X*X*X 先化简再求值:(x+y)(x-y)+(x^2-2xy+y^2)-(x^2y)^3÷(x^2y)^2,其中x=1,y=2. 1.(x-y)(x+y)+(x-y)+(x+y)2.x(x+2)-(x+1)(x-1),其中x=-二分之一请写清步骤,结果. (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 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) y=(2x*x-2x+3)/(x*x-x+1),求值域? 求值域 1,y=(x+2)/(x*x+3x+6) 2,y=3x/(x*x+4) 若2x-3y+4=0则x（x*x-1)+x(5-x*x)-6y+7