take 3 bit numbers.. below are the range of 2's complment numbers that can be represented with 3bits
LHS is 2's complement representation of number in RHS
001-1
010-2
011-3
000-0
111- -1
110- -2
101- -3
100- -4
2's complement representation of -1 in 3 bits = 111
2's complement of -1 is = 2's complement of (111) = 001