Chun is incorrect. He made a mistake in step 2
Let's look at the term 3(2x-1)^2
Once we factor, we have
[tex]\begin{gathered} 3\cdot(2x-1)^2=3\cdot(2x-1)\cdot(2x-1) \\ =(6x-3)\cdot(2x-1) \end{gathered}[/tex]He made a mistake solving the product in step 2