This document discusses complex numbers. It defines the imaginary unit i as the number whose square is -1. Complex numbers are expressed as a + bi, where a is the real part and bi is the imaginary part. All real number properties extend to complex numbers. Operations like addition, subtraction, multiplication, division and powers of i are demonstrated. Complex conjugates are used to simplify expressions and divide complex numbers. Examples are provided to simplify expressions and perform operations on complex numbers.