已知,xy/(x+y)=1,zy/(z+y)=2,zx/(x+z)=3,球x=?
问题描述:
已知,xy/(x+y)=1,zy/(z+y)=2,zx/(x+z)=3,球x=?
答
(xy)/(x+y)=1,则:(x+y)/(xy)=1,即1/x+1/y=1.同理,有:1/y+1/z=1/2,1/z+1/x=1/3,三个方程相加,得:2(1/x+1/y+1/z)=1+1/2+1/3=11/6,则1/x+1/y+1/z=11/12,因1/y+1/z=1/2,则1/x=5/12,则x=12/5...