complex number

A complex number is a combination of two numbers, usually written in the form of a+bi. The a is referred to as the real part, and bi is referred to as the imaginary part. The imaginary part bi can be thought of as a number that is not really there, but it is used to help with calculations. For example, the square root of -1 is the imaginary number i, which is equal to 0 + 1i. Complex numbers can be used to solve equations that regular numbers cannot.