Question

what makes this integral improper integral o to - infinity e^(x)/1+e^x

Answer 1

Hm... Is there a limit in that problem?

Answer 2

Can you write down the question using the equation box so we can see what it actually looks like. I don't quite understand what you're asking. If you mean this:\[\int\limits_{0}^{\infty} e^x/(1+e^x)\]
By definition of an improper integral, if one of the bounds is infinity or negative infinity, it's an improper integral because infinity isn't a real number.