Ex: Find Values Where a Rational Expression is Undefined

This video provides three examples of how to determine the values where a rational expression is undefined.

[sebastian]

wait so you do nothing with the top???

[jeremiahtoller]

I DID find this helpful, thanks. (This vid might benefit from a re-do; there's a gnarly hum and lack of visual focus through large portions of the video).

[jakeyoung]

The 4 just magically disappears? I am confused.

[Astroweasels]

But what about the 9 in the I know you said 10-1 =9 but how is that getting rid of it? don't you still have to address it?