Give an example of a real number, an imaginary number, and a complex number. Explain how you know what type each one is.

Real number:
Imaginary Number:
Complex number:

1 answer

Sure! Here’s an example of each type of number, along with explanations for how we classify them:

Real number:
Example: \( 3.14 \)
Explanation: A real number is any number that can be found on the number line, including both rational numbers (like integers and fractions) and irrational numbers. The number \( 3.14 \) is a rational number because it can be expressed as a fraction (\( \frac{314}{100} \)). It does not have an imaginary part.


Imaginary number:
Example: \( 5i \)
Explanation: An imaginary number is defined as a number that can be written as a real number multiplied by the imaginary unit \( i \), which is the square root of -1. The number \( 5i \) is purely imaginary because it is composed only of the imaginary unit \( i \) and has no real part (the real part is \( 0 \)).


Complex number:
Example: \( 2 + 3i \)
Explanation: A complex number is defined as a number that has both a real part and an imaginary part and can be expressed in the form \( a + bi \), where \( a \) is the real part and \( b \) is the coefficient of the imaginary part. In this example, \( 2 + 3i \) has a real part \( 2 \) and an imaginary part \( 3i \), making it a complex number.

To summarize:

  • Real number: \( 3.14 \) (no imaginary part)
  • Imaginary number: \( 5i \) (no real part)
  • Complex number: \( 2 + 3i \) (has both real and imaginary parts)