​ this is my answer (Just checking my answers) not here to just get answers..

It says waiting for moderation. 

     -4y² + 3xy - 12y + 9x

=

     y(-4y + 3x) + 3(-4y + 3x)

=

     (-4y + 3x)(y + 3)

=

     (3x - 4y)(y + 3)