# Homework Help: Complex numbers

1. May 14, 2012

### robertjford80

1. The problem statement, all variables and given/known data

solve the following and determine if it is complex, real and/or imaginary

x2 = 1

3. The attempt at a solution

The answer is x = +-1 which I agree with but the book says that that is complex and real. How complex? Complex numbers have the form a + bi, there's no bi in that answer.

2. May 14, 2012

### scurty

$\mathbb{R} \subseteq \mathbb{C}$

A complex number $c$ can represented as $c = a + bi$ where $a,b \in \mathbb{R}$

In this case, b=0. A purely imaginary number is when a=0.

3. May 14, 2012

### SteveL27

They're trying to get you to see that real numbers are complex numbers. But it's a little misleading, since clearly if someone asks if 1 is "real or complex," the answer is real ... even though technically, the right answer is "both." I think this is a bit of a trick question.

4. May 14, 2012

### robertjford80

thanks, I did feel tricked, but I get the point now.