Answer :
[tex]y=\mleft(x-3\mright)^2-3\mleft(x-4\mright)[/tex][tex]\begin{gathered} y=x^2-6x+9-3x+12 \\ \end{gathered}[/tex]
we reduce the equal terms and we obtain the answer is
[tex]y=x^2-9x+21[/tex]