##### Like what you saw?

##### Create FREE Account and:

- Watch all FREE content in 21 subjects(388 videos for 23 hours)
- FREE advice on how to get better grades at school from an expert
- Attend and watch FREE live webinar on useful topics

# Symmetry of Graphs: Odd and Even Functions - Problem 1

###### Norm Prokup

###### Norm Prokup

**Cornell University**

PhD. in Mathematics

Norm was 4th at the 2004 USA Weightlifting Nationals! He still trains and competes occasionally, despite his busy schedule.

How do you prove that a function is even or odd? Let’s start with some examples. Is this function odd, even or neither. Well you may have some intuition about whether it’s odd, even or neither but often your teacher will want you to actually prove the result.

The way to do that is to start by plugging in –x. f(-x) equals –x minus .04 minus (-x)³. -x³ is well the opposite of x³ is (-x)³ and so that’s going to change this to plus .04x³ and I can factor the minus sign out of the whole thing. I get –(x -.04x³). Of course this is just f(x). For f(-x) to equal –f(x), that’s the very definition of am odd function. So we conclude, f is odd.

Let’s do another example. Here we have g(x) equals 25 over x² plus 9. Again just plug in -x. We get 25 over -x² plus 9. The quantity (-x) ² is the same as x². This is exactly the same as 25 over x² plus 9. And this is exactly g(x). For g(-x) to equal g(x) is the very definition of an even function. So we conclude that g is even.

Remember if you’re proving a function even or odd, always start by plugging in –x and see if you can algebraically manipulate the expression into g(x) or its opposite, to prove whether a function is even or odd.

Please enter your name.

Are you sure you want to delete this comment?

###### Norm Prokup

PhD. in Mathematics, University of Rhode Island

B.S. in Mechanical Engineering, Cornell University

He uses really creative examples for explaining tough concepts and illustrates them perfectly on the whiteboard. It's impossible to get lost during his lessons.

Thiswas EXCELLENT! I am a math teacher and have been looking for an easy/logical way to explain the lateral area of a cone to my students and this was incredibly helpful, thank you very much!”

I just learned more In 3 minutes of polygons here than I do in 3 weeks in my math class”

Hahaha, his examples are the same problems of my math HW!”

##### Sample Problems (3)

Need help with a problem?

Watch expert teachers solve similar problems.

## Comments (0)

Please Sign in or Sign up to add your comment.

## ·

Delete