Re: Why is equation set can't solve in Mathematica?

• To: mathgroup at smc.vnet.net
• Subject: [mg99721] Re: Why is equation set can't solve in Mathematica?
• From: "Sjoerd C. de Vries" <sjoerd.c.devries at gmail.com>
• Date: Tue, 12 May 2009 03:09:00 -0400 (EDT)
• References: <gu8ugp\$6sm\$1@smc.vnet.net>

```Perhaps you didn't wait long enough... I didn't have the time or
patience either.

But, let's have a closer look.

There are two equations for yx13b, so we may equate both right-hand
sides and solve for yx13a. It takes a couple of minutes and then
Mathematica finds a some huge answers (and a small one, 0). If you
enter these in the original equations you'll have yx13b.

Cheers -- Sjoerd

On May 11, 12:26 pm, Weber <a.pengw... at gmail.com> wrote:
> Hi, all. This problem is annoying
> This:
>
> Solve[{yx13b == (-dg sxa yx13a +
>     Sqrt[-dg dx1 sxa^2 yx13a + dg px013a sxa^2 yx13a -
>      dg hxa sxa^2 yx13a^2 - dg sxa vx13a yx13a^2])/(dg sxa),
>   yx13b == (-dx3 sxb + px013b sxb - 2 dg sxb yx13a - Sqrt[
>     4 dg sxb (-dg sxb - hxb sxb - vx13b) yx13a^2 + (-dx3 sxb +
>        px013b sxb - 2 dg sxb yx13a)^2])/(
>    2 (dg sxb + hxb sxb + vx13b))}, {yx13a, yx13b}]
>
> can't solve. Why?

```

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