Algebra II

Advanced algebraic concepts including polynomials, rational expressions, and complex numbers.

Advanced Topics

Complex Numbers and Imaginary Units

Enter the Imaginary World

Sometimes, equations don't have real-number solutions—like \( x^2 + 1 = 0 \). That's where complex numbers come in!

What Are Complex Numbers?

A complex number is written as \( a + bi \), where:

  • \( a \): real part
  • \( b \): imaginary part
  • \( i \): imaginary unit, where \( i^2 = -1 \)

Operations

You can add, subtract, multiply, and even divide complex numbers. Just treat \( i \) like a variable, but remember \( i^2 = -1 \).

Why Use Complex Numbers?

Complex numbers help solve equations that have no solutions in the real number system and are used in fields like engineering and physics.

Visualizing Complex Numbers

You can plot complex numbers on a special graph called the complex plane, with the real part on the x-axis and the imaginary part on the y-axis.

Key Formula

\[i^2 = -1\]

Examples

  • Adding \( (2 + 3i) + (1 - 4i) = 3 - i \)

  • Multiplying \( (1 + i)(1 - i) = 1 - i^2 = 2 \)

In a Nutshell

Complex numbers extend the real numbers by including solutions to equations like \( x^2 + 1 = 0 \).

Key Terms

Imaginary Unit
The symbol \( i \) where \( i^2 = -1 \)
Complex Plane
A graph with a real and imaginary axis to plot complex numbers
Complex Numbers and Imaginary Units - Algebra II Content | Practice Hub