Re: Series[] command

• To: mathgroup at smc.vnet.net
• Subject: [mg55945] Re: [mg55939] Series[] command
• From: DrBob <drbob at bigfoot.com>
• Date: Mon, 11 Apr 2005 03:14:54 -0400 (EDT)
• References: <200504110307.XAA06466@smc.vnet.net>
• Sender: owner-wri-mathgroup at wolfram.com

```Both answers are equivalent:

Normal@Series[a b,{b,mb,2},{a,ma,2}]
%==ma*mb+ma(b-mb)+mb(a-ma)+(a-ma)(b-mb)//Simplify

b (a-ma)+ma (b-mb)+ma mb

True

Series calculates the series expansion one variable at a time, and that's probably why it doesn't give the expression you expect.

Bobby

On Sun, 10 Apr 2005 23:07:18 -0400 (EDT), Kris Preacher <preacher at unc.edu> wrote:

> Hi all,
>
> I need to obtain the second-order Taylor series expansion of a*b around the
> points ma and mb. I thought Mathematica's Series[] command would do the
> trick, but no. The correct answer is:
>
> ma*mb + ma(b-mb) + mb(a-ma) + (a-ma)(b-mb)
>
> Mathematica gives:
>
> b(a-ma) + ma(b-mb) + ma*mb
>
>
> Thanks,
> Kris Preacher
> UNC
>
>
>
>
>

--
DrBob at bigfoot.com

```

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