Ratios of LCM and GCD
Source: 1972 USAMO Problem 1
March 6, 2010
number theoryleast common multiplegreatest common divisorAMCUSA(J)MOUSAMO
Problem Statement
The symbols and denote the greatest common divisor and least common multiple, respectively, of the positive integers . For example, (3,6,18)\equal{}3 and [6,15]\equal{}30. Prove that \frac{[a,b,c]^2}{[a,b][b,c][c,a]}\equal{}\frac{(a,b,c)^2}{(a,b)(b,c)(c,a)}.