two non zero numbers : m & n
m + n =0
1) m & n are odd - Never true

2) m & n are positive - never true

3) m and are negative- never true

4) Im is equal to Inl.- Always true

5) |m| is not equal to |n|- Never true

6) m is positive and n is negative. - Sometimes true
If m is equal to n then:
+m + (-n) = m-n =0