One can think of them as an ordered pair of numbers. Complex numbers helped earlier mathematicians deal with the problem of taking the square root of a negative number. A complex number takes the form a + b*sqrt(-1), where a and b are real numbers.
Numbers that can be written in the for a + b, for example, 2.7 + 8.9i, where a and b are real numbers and i = .
Numbers composed of a real number part and an imaginary number part.