\( 15 m^{4} n^{4}+6 m n^{3}+3 m^{2} n^{2} \)
\(\displaystyle =m\cdot n^{2}(15m^{3}n^{2}+3\cdot 2n+3m)\)
Step 1 :\(\displaystyle \text{Factor out } m\cdot n^{2} \text{ from the expression:} \)
Step 2 :\(\displaystyle =m\cdot n^{2}(15m^{3}n^{2}+6n+3m)\)
Step 3 :\(\displaystyle =m\cdot n^{2}(15m^{3}n^{2}+3\cdot 2n+3m)\)