# If the difference of two variables is finite.....

• Aug 12th 2011, 12:58 AM
fallingleaves75
If the difference of two variables is finite.....
If the difference of two variables is finite, can you assume that each of the variables themselves are finite??

for instance, if x - y < infinity, can you assume that both x and y are finite?

thanks for the help!
• Aug 12th 2011, 01:09 AM
Siron
Re: If the difference of two variables is finite.....
You've an undefined form $\displaystyle \infty-\infty$, what you can say is:
$\displaystyle \infty-a=\infty$ where $\displaystyle a\in \mathbb{R}$
$\displaystyle a-\infty=-\infty$ where $\displaystyle a\in \mathbb{R}$

If two variables are finite then their difference is finite.
• Aug 12th 2011, 01:39 AM
CaptainBlack
Re: If the difference of two variables is finite.....
Quote:

Originally Posted by fallingleaves75
If the difference of two variables is finite, can you assume that each of the variables themselves are finite??

for instance, if x - y < infinity, can you assume that both x and y are finite?

thanks for the help!

If their difference is defined then both must be defined.

CB