# Thread: What is an undefined value? (see question inside)

1. ## What is an undefined value? (see question inside)

Started a new online course to try and get better at math, but the course has a few dead links and I'm missing some information. I have this question:

"For what values are the following undefined"

x^2 - 2x + 3
___________
x^2+2x+1

first I expand

x^2- 2x + 3
__________
(x+1)(x+1) [or x+1^2]

Then I don't know what to do.

I've looked at the easier examples they give me and when they give an answer for an "undefined value" it is the x-intercepts/zeros of the function. Can someone explain to me what exactly they mean by "undefined values"

2. ## Re: What is an undefined value? (see question inside)

The original equation is undefined if the denominator = 0. So in this case it's undefined if $x^2+2x+1 = 0$, which as you demonstrated means it's undefined if $(x+1)^2 = 0$. For what value(s) of x does $(x+1)^2 = 0$?

3. ## Re: What is an undefined value? (see question inside)

Okay that makes more sense, im not sure if I'm understanding that last part right but does x=-1. I'm not sure how to phrase the answer

4. ## Re: What is an undefined value? (see question inside)

Right - you say the function is undefined for x = -1. To test this, try putting -1 in place of x in the denominator of the original equation - if the denominator turns out to be 0, then the function is undefined at that point.