- #1
mr_garlic
- 8
- 0
Homework Statement
[tex]\lim_{x\rightarrow\infty} \sqrt{e^{2x}+9}-e^x[/tex]
Homework Equations
[tex]\lim_{x\rightarrow\infty} \sqrt{x} = \infty[/tex]
[tex]\lim_{x\rightarrow\infty} e^x = \infty [/tex]
The Attempt at a Solution
[tex]\lim_{x\rightarrow\infty} \sqrt{e^{2x}+9}-e^x = \lim_{x\rightarrow\infty} \frac{e^{2x}+9-e^{2x}}{\sqrt{e^{2x}+9}+e^x}[/tex]
[tex]=\lim_{x\rightarrow\infty} \frac{9}{\sqrt{e^{2x}+9}+e^x}[/tex]
The limit as x>infty of sqrt(x) is infty
the limit as x>infty of e^2x is infty
the entire bottom term tends towards infinity as x tends towards infinity
therefore
[tex]\lim_{x\rightarrow\infty} \frac{9}{\sqrt{e^{2x}+9}+e^x}=0[/tex]
My professor had a different answer that we didn't have time to go over in class, and my answer just doesn't feel right. Where did I make my mistake?