[tex]\displaystyle{ \frac{y^2-16}{4y-16} \div \frac{y+4}{16y}= \frac{y^2-16}{4y-16}\cdot\frac{16y}{y+4}\\\\[/tex]
[tex] \displaystyle{ = \frac{y^2-4^2}{4(y-4)} \cdot\frac{16y}{y+4}= \frac{(y-4)(y+4)}{4(y-4)}\cdot\frac{16y}{y+4} = \frac{16y}{4}=4y [/tex]
Answer: 4y
Remark: [tex]y^2-4^2=(y-4)(y+4)[/tex] by the difference of squares identity, or formula.
