\[(3x - 5)^{2} - (x + 3)^{2} =\]
\[= (2x - 8)(4x - 2) =\]
\[= 2 \cdot (x - 4) \cdot 2 \cdot (2x - 1) =\]
\[= 4 \cdot (x - 4)(2x - 1)\]