Problem using flalign (LaTeX)

Question

I am trying to put 3 equations with aligned "=" signs as well as left aligned. I tried the following:

\documentclass{article}
\usepackage{amsmath}
\begin{document}

\begin{flalign*}
RPC &= A+B\tilde{f} +C x  &\\
A   &= a+\eta             &\\
E   &= cte                &
\end{flalign*}

\end{document}

With this, I get the material on the left and the alignment signs "=". However, I also need A (in the second equation) and E (in the third equation), which must be aligned with R (in the first)

Does anyone know how to get it?

thank

Answer 1

This approach avoids explicit space commands.

\begin{flalign*}
RPC          &= A+B\tilde{f} +C x  &\\
\omit$A$\hfil&= a+\eta             &\\
\omit$E$\hfil&= cte                &
\end{flalign*}

This method is slightly smaller than TeXish.

\begin{flalign*}
\rlap{$RPC$}\phantom{RPC} &= A+B\tilde{f} +C x  &\\
\rlap{$A$  }\phantom{RPC} &= a+\eta             &\\
\rlap{$E$  }\phantom{RPC} &= cte                &
\end{flalign*}

Answer 2

& , . , , \hphantom, A E RPC:

\documentclass{article}
\usepackage{amsmath}
\begin{document}

\begin{flalign*}
RPC            & = A+B\tilde{f} +C x  \\
A\hphantom{PC} & = a+\eta \\
E\hphantom{PC} & = cte
\end{flalign*}

\end{document}

Answer 3

Try to execute

\begin{flalign*}
& RPC &{}={}& A+B\tilde{f} +C x  &\\
& A   &{}={}& a+\eta             &\\
& E   &{}={}& cte                &
\end{flalign*}

Notes: 1. The {} icon around the equal sign is necessary to give it something space itself. 2. In a soft environment, the fields alternately creep to the right, and then the flash drive. We can analyze one of the above lines using →> and <to display the direction of the flash

  & RPC & {}={} & A+B\tilde{f} +C x &     \\
>   <<<   >>>>>   <<<<<<<<<<<<<<<<<   >>>

Answer 4

The farther, the more elegant, but this is a trick:

\documentclass{article}
\usepackage{amsmath}
\begin{document}
\begin{minipage}{0pt}
\begin{flalign*}
 & RPC & &\mspace{-22.0mu} = A+B\tilde{f} +C x  \\
 & A   & &\mspace{-22.0mu} = a+\eta             \\
 & E   & &\mspace{-22.0mu} = cte              

\end{flalign*}
\end{minipage}
\end{document}

Answer 5

Thanks guys. This seems to give some good results:

\documentclass{article}
\usepackage{amsmath}
\begin{document}
\begin{flalign*}
RPC\hphantom{AE}   & \mspace{-30.0mu}= A+B\tilde{f} +C x  & \\
A  \hphantom{RPCE} & \mspace{-30.0mu}= a+\eta             &\\
E  \hphantom{RPCA} & \mspace{-30.0mu}= cte                &
\end{flalign*}
\end{document}