a.b/a+b=b.c/b+c=c.a/c+a=a^2+b^2+c^2/(a+b).(b+c)(c+a)=a^2/c+a=b^2/b+c=c^2/a+b
c.a/c+a=a^2/c+a suy ra :ac=a^2(cùng mẫu)
.......................................bc=b^2
.......................................ab=c^2
M=ab+2bc+2017ca/2017ca+2bc+ab=1
Hoặc ab/a+b=bc/b+c=ca/c+a
suy ra:a+b/ab=b+c/bc=c+a/ca
suy ra a/ab+b/ab=b/bc+c/bc=c/ca+a/ca
1/b+1/a=1/c+1/b=1/a+1/c
suy ra :1/a=1/b=1/c
a=b=c Suy ra:ac=a^2;bc=b^2;ab=c^2