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MathGroup Archive 1997

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Re: Help me please!!!

  • To: mathgroup at smc.vnet.net
  • Subject: [mg5801] Re: [mg5770] Help me please!!!
  • From: Dave Snead <dsnead at pacbell.net>
  • Date: Wed, 22 Jan 1997 00:44:10 -0500
  • Organization: Saguaro Software
  • Sender: owner-wri-mathgroup at wolfram.com

Cyberman wrote:
> 
> Hello. I've a little problem:
> 
> I must invert this function: y = (x^2) + x     for x >= 0
> 
> Is there anybody that could help me?
> 
> Thanx.
> 
>    +---------------------------------------+
>    /   - - ---> C y b e r M a n <--- - -   /
>    /    _______ Milano -- ITALY _______    /
>    /->>> e-mail:  cyberman at zerocity.it <<<-/
>    /          PGP KeyID: 487C6475          /
>    +---------------------------------------+
>         - ----< Key fingerprint >---- -
> 8F 50 99 35 BF A4 83 6C 68 11 C9 31 DC A7 65 F2
>       <---------------- at ----------------->


Use Solve

In[7]:=Solve[y == (x^2) + x,x]

Out[7]:={{x -> (-1 - Sqrt[1 + 4*y])/2}, 
         {x -> (-1 + Sqrt[1 + 4*y])/2}}

Use the 2nd solution, since y >= 0 gives x >= 0.


Dave Snead
dsnead at pacbell.net


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