Question

如图（点图放大）1. 302. a+b+c

Answer 1

原式=a(a+b)(a-5b)/a(a-b))(a-5b)=(a+b)/(a-b)

a/(a-b)=2,即a=2b,代入后得3.

x/(1+x)+y/(1+y)+z/(1+z)=1/((1/x)+1)+1/((1/y)+1)+1/((1/z)+1)

=1/((a+b)/c+1)+1/((b+c)/a+1)+1/((c+a)/b+1)

=(a+b+c)/(a+b+c)=1