MathDB
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 (a,b,,g) (a,b,\ldots,g) and [a,b,,g] [a,b,\ldots,g] denote the greatest common divisor and least common multiple, respectively, of the positive integers a,b,,g a,b,\ldots,g. 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)}.