Given, \[3x\text{ }\text{ }4\]is a factor of g(x) = \[\mathbf{3}{{\mathbf{x}}^{\mathbf{2}}}~+\text{ }\mathbf{2x}\text{ }\text{ }\mathbf{k}\].
So, \[f\left( 4/3 \right)\text{ }=\text{ }0\]
\[\begin{array}{*{35}{l}}
3{{\left( 4/3 \right)}^{2}}~+\text{ }2\left( 4/3 \right)\text{ }\text{ }k\text{ }=\text{ }0 \\
16/3\text{ }+\text{ }8/3\text{ }\text{ }k\text{ }=\text{ }0 \\
24/3\text{ }=\text{ }k \\
k\text{ }=\text{ }8 \\
\end{array}\]