# Rational limit involving e?

• January 26th 2010, 09:13 AM
nautica17
Rational limit involving e?
Need some help with this one:

lim x-> inf of (1-e^x) / (1+e^x)

The answer should be -1 but I don't get how that is so. When you plug in infinity you get -inf/inf right? How does this problem work out algebraically?
• January 26th 2010, 09:17 AM
Krizalid
$\frac{1-e^{x}}{1+e^{x}}=\frac{e^{-x}-1}{e^{-x}+1},$ can you compute its limit now?
• January 26th 2010, 09:21 AM
nautica17
Quote:

Originally Posted by Krizalid
$\frac{1-e^{x}}{1+e^{x}}=\frac{e^{-x}-1}{e^{-x}+1},$ can you compute its limit now?

Thank-you! I get it now! :)