Math & Science ⇒ eqnarray*: writing text aligned right from equations

[panard]

Hello,

I would like to write some text flushed at right of equations :

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equation1              first comment in text
equation2 and 3               second comment

I tried something like

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\begin{eqnarray*}
equation1 \hfill\text{first comment in text}\\
equation2 and 3 \hfill\text{second comment}
\end{eqnarray*}

but it doesn't work (no space is insered).

Any help?
I tried to understand how equations numbers are put at right, but the code looks too complex for me...

Thx

[localghost]

At first please read a paper why not to use the eqnarray environment [1]. The next step is to include the amsmath package and use its align environment. It lets you typeset your equation system with aligned text as desired.

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\begin{align*}
  (a+b)^2&=a^2+2ab+b^2 & \text{Your first comment} \\
  (a-b)^2&=a^2-2ab+b^2 & \text{Second comment} \\
  (a+b)(a-b)^{\hphantom{2}}&=a^2-b^2 & \text{Last comment}
\end{align*}

For more information refer to the manual of the package. Other useful hints are listed in the "Math mode" document.

[1] The PracTeX Journal - Lars Madsen: Avoid eqnarray!


Best regards and welcome to the board
Thorsten¹