The numbers 0-9 are lined up in a row, like this:
0 1 2 3 4 5 6 7 8 9
You have to put in + and - signs in the blanks, so that in the end it will all equal 1.
Also, if possible, try to make expressions resulting in 0 and -1.
(In reply to re(3): Solution
Since 0 is on the extreme left and we are required to put in + sign and - sign in the 'blanks', we don't have the option of assigning a 'minus' to 0.
Hence 0 must always remain in the complimentary (+ sign) subsets. The presence of 0 in any main (- sign) subset would render the subset 'unminussable'.
So, there will be only 23 subsets.
But I take DJ's point. I should've added the 'non-zero' or 'minussability' criteria while defining the subsets.
Posted by Sanjay
on 2003-05-23 14:28:47