Exercise & Solution Page

Question

In an earlier post of mine, I asked how to create separate exercise and solution pages for basic arithmetic. I'm trying the same thing now for factoring simple trinomials, but it's not working and I'm not sure why. I feel like the key parts of the code - defining the exercise page and the solution page - are basically the same, but they obviously are not since my code does not compile.

I do know that if I comment out the line in the body \FactoredPage, it compiles, though I still get minor error messages.

What's happening?

\documentclass{article}

\usepackage{pgf}
\usepackage{pgffor}

\setlength{\parindent}{0pt}

\pagestyle{empty}

\pgfmathsetseed{\number\pdfrandomseed}

\newcommand{\InitVariablesSTA} %all positives
{%
 \pgfmathsetmacro{\avar}{int(1)}
 \pgfmathsetmacro{\bvar}{int(random(1,11))}
 \pgfmathsetmacro{\cvar}{int(1)}
 \pgfmathsetmacro{\dvar}{int(random(1,11))}

 \pgfmathsetmacro{\Avar}{int(\avar*\cvar)}
 \pgfmathsetmacro{\Bvar}{int(\avar*\dvar+\bvar*\cvar)}
 \pgfmathsetmacro{\Cvar}{int(\bvar*\dvar)}
}

\newcommand{\STA}
{%
 \InitVariablesSTA%
 \newcommand{\factored}{\((x+\bvar)(x+\dvar)\)}%
 \newcommand{\expanded}{\(x^2+{\Bvar}x+\Cvar\)}%
}

\newcommand{\FactoredPage}{}

\newcommand{\ExpandedPage}[1]
{%
 \foreach \x in {1,...,#1}
  {%
   \STA \expanded \par
   \xdef\FactoredPage{\FactoredPage \factored \par}%
  }
}


\begin{document}

\ExpandedPage{10}

\FactoredPage

\end{document}

Answer 1

The macros \( and \) don't survive \xdef. Use $:

\newcommand{\STA}
{%
 \InitVariablesSTA
 \newcommand{\factored}{$(x+\bvar)(x+\dvar)$}%
 \newcommand{\expanded}{\(x^2+{\Bvar}x+\Cvar\)}%
}

Related: Build tabular content via \foreach

You might use \protected@xdef, so \( and \) might be used; it's simpler the other way.

Answer 2

Here is, what you need to do. But without any pgf (or similar) package. Only primitives and plain TeX macros are used:

\input random
\newcount\tmpnum  \newcount\loopnum
\randomi=1  % fixed random sequence (independent of time of document processing)
\parindent=0pt

\def\ExpandedPage#1{%
   \def\FactoredPage{}\loopnum=0
   \loop
      \advance\loopnum by1
      \preparepages
      \ifnum\loopnum<#1 \repeat 
}
\def\preparepages{\par
   \setrannum\tmpnum{1}{10} \edef\bvar{\the\tmpnum}
   \setrannum\tmpnum{1}{10} \edef\dvar{\the\tmpnum}
   \tmpnum=\bvar \advance\tmpnum by\dvar  \edef\Bvar{\the\tmpnum}
   \tmpnum=\bvar \multiply\tmpnum by\dvar \edef\Cvar{\the\tmpnum}
   $x^2 + \Bvar x + \Cvar$\par
   \edef\FactoredPage{\FactoredPage$(x+\bvar)(x+\dvar)$\par}
}

\ExpandedPage{10}
\bigskip
\FactoredPage

\bye