Table is showing up too low

I've simplified the code (mainly by reducing the number of minipage environments). The array and the graph are now centered vertically next to each other.

\documentclass[demo]{beamer} % remove 'demo' option in real document
\usepackage{array} % for '\extrarowheight' macro
\begin{document}
\begin{frame}
\frametitle{Example 2}
Complete the table  of values below. Then plot the points on the Cartesian plane.

\bigskip
%\begin{minipage}{0.25\textwidth}
\setlength\extrarowheight{2pt} % for a more "open" look
$\begin{array}{|r|c|} % use 'array' rather than 'tabular' since contents are 'math-y'
\hline
x&y=x^2+1\\
\hline
-1&\mathbf{0}\\ % use '\mathbf', not '\textbf'
\hline
0&\mathbf{1}\\
\hline
1&\mathbf{2}\\
\hline
2&\mathbf{5}\\
\hline
3&\mathbf{10}\\
\hline
\end{array}$
%\end{minipage}%
\hfill 
\begin{minipage}{0.7\textwidth}
\includegraphics[width=\linewidth]{Unit4W1L6-image2.png}
\end{minipage}
\end{frame}
\end{document}

Beamer has columns for that purpose.

\documentclass{beamer}
\begin{document}
\begin{frame}
\frametitle{Example 2}
\begin{overlayarea}{\textwidth}{8cm}
Complete the table  of values below. Then plot the points on the Cartesian plane.
\begin{columns}
\begin{column}{0.30\linewidth}
%\begin{table} %<- do you need that?
\begin{tabular}[t]{|c|c|}
\hline
$x$&$y=x^2+1$\\
\hline
$-1$&\textbf{0}\\
\hline
$0$&\textbf{1}\\
\hline
$1$&\textbf{2}\\
\hline
$2$&\textbf{5}\\
\hline
$3$&\textbf{10}\\
\hline
\end{tabular}
%\end{table}
\end{column}
%\hfill
\begin{column}{0.7\linewidth}
\includegraphics[width=\linewidth]{example-image-a}
\end{column}
\end{columns}
\end{overlayarea}
\end{frame}
\end{document}