X+Y=500; X(1+10%)+Y(1+20%)=570 然后解方程得：X=300 Y=200 所以：X(1+10%)=330 Y(1+20%)=240

(x+y)/6+(x-y)/10=1,(x+y)/6-(x-y)/10=5 {6/x+y+10/x-y=30 6/x+y-10/x-y=-1 y'/y=1/x y-x=1 10x+y> 10x+y30 10x+y 已知y/x=9/10则(1-y/x)[x/(y-x)]? x-y/x-x+y/y-(x+y)(x-y)/y² y/x=2 y'-(1/x)y=xe^-x {4x-3y-10=0 3x-2y=0,{3x-4(x-y)=2 2x-3y=1,{2(x+y)-(x-y)=3 (x+y)-2(x-y)=1 x+(9-8-y)=10 y+y-(9-8-y)=2 x-y=xx-9.9x xy=11y-1 y=? x=? x+y-xy=?x+(9-8-y)=10y+y-(9-8-y)=2x-y=xx-9.9xxy=11y-1 y=?x=?x+y-xy=? 化简 x / y(x+y) - y / x(x+y) = (x+y+z)÷10=x+1.1 y+x=z-80+y-1 z-y=8x+y+8 x+z÷y=? 25（x+y)^2+10(y-x)+1=?因式分解 25(x-y)^2+10(y-x)+1= y=ln(1+x),求y^10(x)? 解方程组x+y/6+x-y/10=3,x+y/6+y-x/10=-1x+y/6+x-y/10=3 ①x+y/6+y-x/10=-1 ② x-y/7 - x+y/10 =1/2 2(x-y)-5(x+y)=3修改、、、、（x-y)/7-(x+y)/10=1/2 2(x-y)-5(x+y)=3 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.