Ta co a.c = b2 =b.b
Suy ra a/b =b/c (1)
Ta co a.b=c2=c.c
Suy ra a/c=c/b suy ra c/a = b/c (2)
Tu (1),(2) suy ra a/b=b/c=c/a
Ap dung tinh chat cua day ti so bang nhau ta co
a/b=b/c=c/a=a+b+c/b+c+a=1
Khi do a/b=1 suy ra a=b
b/c=1 suy ra b=c
a/c=1 suy ra a=c
Suy ra a=b=c (3)
Ta co M=b333/a111.c222
Thay (3) vao bieu thuc M ta co
M=a333/a111.a222
=a333/a111+222
=a333/a333 =1
Vay M=1