Which of the following is NOT a real number? (Please explain why!)
(1) -1 (I already ruled out this answers because integers can be real numbers)
(2) square root of 3
(3)square root of -3
(4)0.101001000100001...
Real numbers include rational, irrational, integers, and natural numbers. Real numbers form a subset of complex numbers. So when a number is not real, it is usually complex.
Can you spot a complex number from the list?