Re: cannot solve *trivial* equation
- To: mathgroup at smc.vnet.net
- Subject: [mg34412] Re: cannot solve *trivial* equation
- From: lzhao at ihw.com.cn (Instanton)
- Date: Sat, 18 May 2002 03:51:36 -0400 (EDT)
- References: <ac2n7c$3qr$1@smc.vnet.net>
- Sender: owner-wri-mathgroup at wolfram.com
Hi,
What really astonished me is that you did get a solution in the first
Solve. The reason that you cannot get a solution for S is that
Mathematica assumes only S as a variable, and A and Q are regarded as
independent parameters. Under such conditions you cannot get a
solution by hand either ...
The correct way of solving the system of equations is
Solve[{A == S + Q, Q == 2*S}, {S,A}]
which yields
{S->Q/2, A->3Q/2}
Instanton
Marco Manfredini <marco at technoboredom.net> wrote in message news:<ac2n7c$3qr$1 at smc.vnet.net>...
> Hi,
>
> I just tried a friend's Mathematica 4.0.0.0:
>
> Solve[{A == S + Q, Q == 2*S}, A]
>
> => {A->3*S}
>
> Solve[{A == S + Q, Q == 2*S}, S]
>
> => {}
>
> Can somebody explain this to me? (ie. "bug","you stupid")
>
> Marco