1、x+y=300,x=y+10.2、x-3y=1,x+2y=6.求上面这两道题中x、y的值,

x-y/x-x+y/y-(x+y)(x-y)/y² y/x=2 化简 x / y(x+y) - y / x(x+y) = x(x+y)(x-y)-y(y+x)(y-x)=(x-y)( )填空 x>=1,x-y y=x-1(x y'-(1/x)y=xe^-x y=x(x 1、x+y=300,x=y+10.2、x-3y=1,x+2y=6.求上面这两道题中x、y的值, y'/y=1/x 求导 y=[x/(1+x)]^x 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.y都是自然数,且x(x-u)-y(y-x)+12,求x.y得值快1且x(x-y)-y(y-x)=12 若2/x-1/y=3,求[y/x-y/x-y(x-y/x-x+y)]/x-2y/x的值 y(x+y)+(x-y)²-（x+y）（x-y）,其中x=-1/3,y=3 （x-y)(x+y)-(x+y)^2+2y(y-x),其中x=1,y=3. 2y(x+二分之一y)-[(x+y)(x-y)+2y(y+x)],其中|x-1|=2 x+x+x+x+y+y+y=56 z=0.015x*x+y*x*0.05+(1-x-y)*2.5*(x+y) x>0.35.xy>0.70x+y