[Tex/LaTex] Change the font size of the equation in latex

Question

How can i change the font size of both equation individually?

\begin{eqnarray}
\begin{split}
 % Change the font size
r_j &= 2 \\ 
&\quad + 4
\end{split}
\\
% Change the font size 
r_j = 2 + 4
\end{eqnarray}

I try \scalebox but i got some error. I try :

\begin{eqnarray}
\scalebox{.95}{
\begin{split}
r_j &= 2 \\ 
&\quad + 4
\end{split}
}
\\
\scalebox{.95}{
r_j = 2 + 4}
\end{eqnarray}

Answer 1

Some comments

• The second argument of \scalebox is in text mode by default. To treat it as math material, you need to surround the math material with $ symbols.

• You can't have a split environment inside a scalebox. However, an aligned environment works.

• The eqnarray environment is badly deprecated. Don't use it!! Instead, use either align or gather. In the code below, I use a gather environment as no alignment appears to be performed in your eqnarray-based example.

\documentclass{article} 
\usepackage{amsmath}  % for "gather" and "aligned" environments
\usepackage{graphicx} % for "\scalebox" macro
\begin{document}
\begin{gather}
\scalebox{1.33}{$
   \begin{aligned}
    r_j &= 2 \\ 
        &\quad + 4
   \end{aligned}$} \\
\scalebox{.75}{$
   r_j = 2 + 4$}
\end{gather}
\end{document}