{X-Y=630 {X(1+20%)+Y(1-10%)=(X+Y)(1+12%) 怎么解

y'/y=1/x x-y/x-x+y/y-(x+y)(x-y)/y² y/x=2 y'-(1/x)y=xe^-x 化简 x / y(x+y) - y / x(x+y) = 1=x+y 2=20x+30y 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>=1,x-y y=x-1(x {X-Y=630 {X(1+20%)+Y(1-10%)=(X+Y)(1+12%) 怎么解 1/(x+y)-1/(x-y)=-3/20,2/(x+y)+3/(y-x)=-(1/5)急啊! 集合N=｛（x,y)|（x-1）^2｝+(y-1)^20},M={(x,y)|x^2+y^2 已知x y为实数,且（x+y)(x+y+1)=20 求x+y的值 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 x(x+y)(x-y)-y(y+x)(y-x)=(x-y)( )填空