Ok based on elemental's response, I will go back to my original answer question I proposed to make you think about it: How can you have a derivative at point that DNE?
Hi everyone,
I'm in Calc BC, but this year my teacher seems to make a lot of mistakes. I just wanted to ask a clarifying question about a second derivative of the function below:
I assumed like many of my classmates that we could just do this:
But she said that we had to take into account the original function, and that since there was the as the denominator, we had to include the extra domain restriction of . This doesn't really make sense to me, because I figure you can just reduce it and that shouldn't be a problem. Obviously if the bottom was I would've included the restriction .
Am I right to think this?
Thanks,

Adam