Answer
$z^2-2z-15$.
Work Step by Step
The given expression is
$=(z-5)(z+3)$
Distribute $(z+3)$ to each term of $(z-5)$.
$=z(z+3)-5(z+3)$
Use distributive property.
$=z(z)+z(3)-5(z)-5(3)$
Multiply.
$=z^2+3z-5z-15$
Combine like terms.
$=z^2-2z-15$
Hence, the product is $z^2-2z-15$.
