       Re: Mathematica 6.01 does not know one can not divide by 0??

• To: mathgroup at smc.vnet.net
• Subject: [mg107175] Re: Mathematica 6.01 does not know one can not divide by 0??
• From: David Bailey <dave at removedbailey.co.uk>
• Date: Fri, 5 Feb 2010 03:18:53 -0500 (EST)
• References: <hkean1\$stj\$1@smc.vnet.net>

```zeno wrote:
> I had Mathematica 6.01 try and solve this " equation", and it gives an
> answer back of 5, which if substituted back into the equation, one
> would be dividing by 0. Code and result here...
>
> NSolve[3*x + (1/(x - 5)) == 15 + (1/(x - 5)), x]
> {{x -> 5.}}
>
It is surely not too unreasonable to let NSolve simplify an equality (by
subtracting the term 1/(x-5) from both sides) before solving it. Also,
there is a sense in which 5. is the right answer in the sense that it is
the limit of

Solve[1/(-Q + x) + 3*x == 15 + 1/(-Q + x)] as Q->5

David Bailey
http://www.dbaileyconsultancy.co.uk

```

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