\usepackage{booktabs}
\usepackage{makecell, multirow}
\setcellgapes{3pt}
\begin{table}
\makegapedcells
\begin{tabular}{|c|c|c|c|c|c|c|c|c|}
\hline
\multirow{3}{*}{\textbf{Iterations}}
& \multicolumn{3}{c|}{\textbf{X}}
& \multirow{2.3}{*}{\textbf{$f_{1}$}}
& \multirow{2.3}{*}{\textbf{$f_{2}$}}
& \multirow{2.3}{*}{\textbf{$f_{3}$}}
& \multirow{2.3}{*}{\textbf{$f_{4}$}}
&\multirow{2.3}{*}{\textbf{$f_{5}$}} \\
\cline{2-4}
& \textbf{$x_{1}$}
& \textbf{$x_{2}$}
& \textbf{$x_{3}$}
& & & \\
\hline
\makecell{0}
& 0.45 & 0.10 & 0.10 & 5 &4 &6 &7 &1 \\
\hline
\makecell{1}
& & & & & & & & \\
\hline
\makecell{2}
& 1&2&3 &4 &5 &6 &7 &5 \\
\toprule
\end{tabular}
\end{table}
答案1
\setcellgapes{3pt}
\begin{table}
\makegapedcells
\begin{tabular}{|c|c|c|c|c|c|c|c|c|}
\hline
\multirow{3}{*}{\textbf{Iterations}}
& \multicolumn{3}{c|}{\textbf{X}}
& \multirow{2.3}{*}{\textbf{$f_{1}$}}
& \multirow{2.3}{*}{\textbf{$f_{2}$}}
& \multirow{2.3}{*}{\textbf{$f_{3}$}}
& \multirow{2.3}{*}{\textbf{$f_{4}$}}
& \multirow{2.3}{*}{\textbf{$f_{5}$}} \\
\cline{2-4}
& \textbf{$x_{1}$}
& \textbf{$x_{2}$}
& \textbf{$x_{3}$}
& & &&& \\%<----add
\hline
\makecell{0}
& 0.45 & 0.10 & 0.10 & 5 &4 &6 &7 &1 \\
\hline
\makecell{1}
& & & & & & & & \\
\hline
\makecell{2}
& 1&2&3 &4 &5 &6 &7 &5 \\
\toprule
\end{tabular}
\end{table}