Chapter 11 - Rational Expressions and Functions - 11-2 Multiplying and Dividing Rational Expressions - Practice and Problem-Solving Exercises - Page 674: 35

$-\frac{1}{2}$

Given : $\frac{y-4}{10} \div \frac{4-y}{5}$ This becomes : $\frac{y-4}{10} \times \frac{5}{-(y-4)}$ $= \frac{y-4}{10} \times \frac{5}{-(y-4)}=-\frac{1}{2}$ (After dividing out the common factors $5$ $and$ $(y-4)$)