Dividing by zero
A division by zero is not allowed. It can however occur in a calculation. If you divide a number by zero you will get two results
That is strange.
Explanation
You can approach zero from the positive, then you write x→0+, and you can approach it from the negative, then you write x→0–. So you see
and
This can have tremendous consequences. Look at the one-sided function
and
That is a surprise. We better check this
and