       Re: cubic equation solver

• To: mathgroup at smc.vnet.net
• Subject: [mg130245] Re: cubic equation solver
• From: Peter Pein <petsie at dordos.net>
• Date: Thu, 28 Mar 2013 11:54:58 -0400 (EDT)
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```Am 28.03.2013 09:05, schrieb Elim Qiu:
> x^3 + (=E2=88=9A6 + 2=E2=88=9A3 + 2=E2=88=9A2 -9)x + 2=E2=88=9A3 -=E2=88=9A2 -2 = 0
> has exact roots =E2=88=9A2-2, =E2=88=9A3-=E2=88=9A2, 2-=E2=88=9A3
>
> But Mathematica says:
>
> Solve[x^3 + (Sqrt + 2 Sqrt + 2 Sqrt - 9) x + 2 Sqrt -
>     Sqrt - 2 == 0, x]
>
> {{x -> (1/
>        2 (18 + 9 Sqrt - 18 Sqrt +
>          I Sqrt[3 (4662 - 1252 Sqrt - 1296 Sqrt -
....

Hi,

as parts of your message are unreadable here, I do not know if

In:= Solve[x^3 + (Sqrt + 2*Sqrt + 2*Sqrt - 9)*x +
2*Sqrt - Sqrt - 2 == 0, x] // RootReduce //
Out//InputForm=
{{x -> Sqrt[5 - 2*Sqrt]},
{x -> 2 - Sqrt},
{x -> -2 + Sqrt}}

is what you expect.

Peter

```

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