Paths to a Multinomial Inequality

Arthur T. Benjamin1, Jennifer J. Quinn2
1 DEPARTMENT OF MATHEMatTics, HARVEY Mupp CoLLEGE, 1250 DARTMOUTH Av- ENUE, CLAREMONT, CA 91711
2DEPARTMENT OF MATHEMATICS, OCCIDENTAL COLLEGE, 1600 CAMPUS DRIVE, Los ANGELES, CA 90041.

Abstract

Using path counting arguments, we prove
\(min\{\binom{x_1+x_2+y_1+y_2}{x_1,x_2,(y_1+y_2)},\binom{(x_1+x_2+y_1+y_2)}{(x_1+x_2),y_1,y_2}\}\leq\binom{x_1+y_1}{x_1}\binom{x_1+y_2}{x_1}\binom{x_2+y_1}{x_2}\binom{x_2+y_2}{x_2}\)

This inequality, motivated by graph coloring considerations, has an interesting geometric interpretation.