What are complex numbers? I dont get "a+bi"?

Question

What are complex numbers? I dont get "a+bi"?

Answer 1

i here is the square root of -1. If you think of multiplying by -1 as rotating through 180o, then multiplying by i is like rotating through 90o.

The real numbers give you the number line.  The complex numbers generalise this to give you what is called the complex plane.

Answer 2

They are a number that contains a negative under the radical. When simplified they will contain a whole number "a" and an imaginary number with a coefficient "i" and "b" respectively.

Answer 3

Complex numbers are useful because they are the solution to certain equations and you can get real numbers if you square them.  i is the square root of -1 which is meaningless to most of us, but becomes -1 when squared producing results in electro-magnetic fields and nuclear studies.  And although it is called the imaginary part, it serves a purpose in computing results.