Each cell of a 1997x1997 square grid contains either +1 or -1, with no cell being vacant.
The product of all the numbers in the ith row, and
the product of all the numbers in the ith column are respectively denoted by Ri and Ci.
Prove that Σi=1(Ri + Ci) is always nonzero.
(In reply to a simple proof
by Ady TZIDON)
I think you misread the problem, you have Ri and Ci as the sum of the row/column where in fact they are the products of the row/column.
Posted by Daniel
on 2010-04-29 15:29:54