\[(4x + 2)^{2} - (3x + 2)^{2} =\]
\[= 16x^{2} + 2 \cdot 8x + 4 - \left( 9x^{2} + 2 \cdot 6x + 4 \right) = \ \]
\[= 16x^{2} + 16x + 4 - 9x^{2} - 12x - 4 =\]
\[= 7x^{2} + 4x = x(7x + 4)\text{.\ }\]