# Convergence of Taylor Series

1. Apr 21, 2015

### mmont012

Hello,

For the exercises in my textbook the directions state:

"Use power series operations to find the Taylor series at x=0 for the functions..."

But now I'm confused; when I see "power series" I think of functions that have x somewhere in them AND there is also the presence of an n.

Here is the first problem in the section:

1. The problem statement, all variables and given/known data

xex

Where do I go from here? There isn't an n in the function at all, so the ratio/root test won't help.

If someone could start me off in the right direction I would much appreciate it! I'm just confused at where to start...

Thank you.

2. Apr 21, 2015

### LCKurtz

Do you know or can you calculate the series expansion of $e^x$? You could multiply it by $x$.

3. Apr 21, 2015

### mmont012

Is that all that you do? I wanted to do that but I thought that it was more complicated... well that is super easy then. Why do they mention power series operations? This was the part that was confusing me the most.

4. Apr 22, 2015

### mmont012

And thank you so much for helping me!

5. Apr 22, 2015

### LCKurtz

Yes, it's a pretty trivial example. A better one would be with a higher power of $x$ like maybe $x^{10}e^x$. That would be just as easy using this method compared to doing its Taylor expansion with all those product derivatives.