A good answer might be:

The positive integer: 0000 0110     ( 610 )

Reflect each bit:     1111 1001

Add one:              1111 1010     ( -610 )

Negative Six Again

This resulted in the same repn for minus six as we figured out before. Here is what is going on: When each bit of a pattern is reflected then the two patterns added together make all 1's. This works for all patterns: 

      0110 1010   pattern
      1001 0101   pattern reflected
      ---------
      1111 1111   all columns filled

Adding one to this pattern creates a pattern of all zero's: 

     11111 111    row of carry bits
      1111 1111   all columns filled
      0000 0001   one
      ---------
      0000 0000

But instead, the one is added to the "pattern reflected." 

pattern +  pattern reflected               = all ones

pattern +  pattern reflected + one         = all zeros

pattern + (pattern reflected + one )       = all zeros

pattern + (two's complement of pattern)    = all zeros

Don't be too upset if the above is confusing. Mostly all you need is to get used to this stuff. Of course, this takes practice.

QUESTION 18:

What is the two's complement of 0100 0111?