Note that it is very difficult to see that this equation is a perfect square by inspection. A few short comments about complex numbers are appropriate here. As we saw in the Quadratic Theory section, some quadratics do not cross the x-axis at all. For example, the quadratic never gets closer than 1 to the x-axis, and so has no real zeros at all. However, if we try to solve it anyway, The symbol ' i' is an abbreviation for the square root of minus one , and is called the imaginary unit .
Every complex number has a complex conjugate where the sign of the imaginary part is reversed.
College Algebra A simplified and updated version of the classic Schaum's Outline.