若1/x+1/y=2,则 x/(3x+3y)+(y+2xy)/(3x+3y)=
问题描述:
若1/x+1/y=2,则 x/(3x+3y)+(y+2xy)/(3x+3y)=
答
x/(3x+3y)+(y+2xy)/(3x+3y)=
(x+y+2xy)/3(x+y)=1/3+2/3(xy/x+y)=
1/3+2/3[1/(1/x+1/y)]=1/3+1/3=2/3