Resposta:
[tex]3y^2-12y+12[/tex]
Explicação passo a passo:
[tex](2y-4)^{2}-(y+2)^{2}\\\\(2y-4)^{2}=(2y)^2-2\times 2y\times4+4^2=4y^2-8y+16\\\\\\(y+2)^{2}=y^2+2\times y \times 2 + 2^2=y^2+4y + 4\\\\Resposta: (2y-4)^{2}-(y+2)^{2} =\\4y^2-8y+16-(y^2+4y + 4)=\\ 4y^2-8y+16-y^2-4y - 4=\\3y^2-12y+12[/tex]