Question

Which of the following has no solution?

Answer 1

{x | x < 0} and {x | x > 0}  NO SOLUTION   (look at the picture)

There is no number that is both positive and negative.

{x | x ≤ 0} and {x | x ≥ 0} SOLUTION: the number 0

{x | x ≤ 0} or {x | x ≥ 0}  SOLUTION: all real numbers