Chapter 6 - Section 6.4 - Dividing Polynomials: Long Division and Synthetic Division - Exercise Set - Page 370: 8

$y+2$

Factoring the expressions and cancelling the common factors between the numerator and the denominator, the given expression, $ (y^2+7y+10)\div(y+5) ,$ simplifies to \begin{array}{l}\require{cancel} \dfrac{y^2+7y+10}{y+5} \\\\= \dfrac{(y+5)(y+2)}{y+5} \\\\= \dfrac{(\cancel{y+5})(y+2)}{\cancel{y+5}} \\\\= y+2 .\end{array}