Chapter 6 - Section 6.1 - Rational Expressions and Functions; Multiplying and Dividing - Exercise Set - Page 414: 37

$\frac{y+7}{y-7}$.

The product of a binomial sum and a binomial difference is: $(A+B)(A-B)=A^2-B^2$. The square of a binomial difference is: $(A-B)^2=A^2-2AB+B^2$. Hence here: $\frac{y^2-49}{y^2-14y+49}=\frac{y^2-7^2}{y^2-2\cdot y\cdot7+7^2}=\frac{(y+7)(y-7)}{(y-7)^2}=\frac{y+7}{y-7}$.