Download College Algebra

College Algebra
1.4 Complex Numbers
Objective: add, subtract, multiply and
divide complex numbers
Complex Numbers
Complex Set of Numbers
a + bi
Real
Imaginary
Adding / Subtracting
Complex numbers can be added or
subtracted by adding or subtracting like
parts – real to real and imaginary to
imaginary.
Examples (5 – 2i) + (3 + 3i)
(2 + 6i) – (12 – i)
Multiplying
Complex numbers can be multiplied by using
distributive property or by the FOIL method.
***Remember i2 = -1***
Examples 7i(2 – 9i)
(5 + 4i)(6 – 7i)
Dividing
To divide complex numbers, we have to multiply
by the conjugate of the denominator.
The conjugate of a + bi is a – bi.
Example
Divide
5  4i
.
4i
Conjugate = 4 + i.
Practice