x+y=480 (1+10%)x+(1+20%)y=554

(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-x=1 10x+y> 10x+y30 10x+y 已知y/x=9/10则(1-y/x)[x/(y-x)]? x>=1,x-y y=x-1(x 求导 y=[x/(1+x)]^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 y'-(1/x)y=xe^-x z=0.015x*x+y*x*0.05+(1-x-y)*2.5*(x+y) x>0.35.xy>0.70x+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 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 1.5（x+y）+3（x-y）=27（x+y）-3（x-y）=-62.x-y/7 - x+y/10 =1/22(x-y)-5(x+y)=3所谓细节决定成败, 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