## Introductory Algebra for College Students (7th Edition)

$4y+12$
Step by step multiplication of rational expressions: 1. Factor completely what you can 2. Reduce (divide) numerators and denominators by common factors. 3. Multiply the remaining factors in the numerators and multiply the remaining factors in the denominators. $(\displaystyle \frac{P}{Q}\cdot\frac{R}{S}=\frac{PR}{QS})$ --- Factor what we can: $y^{2}-9=y^{2}-3^{2}=\qquad$... a difference of squares, $=(y+3)(y-3)$ The problem becomes $...=\displaystyle \frac{(y+3)(y-3)\cdot 4}{(y-3)}\qquad$... divide out the common factors $=\displaystyle \frac{(y+3)\fbox{$(y-3)$}\cdot 4}{\fbox{$(y-3)$}}$ $=\displaystyle \frac{(y+3)\cdot 4}{1}$ = $4y+12$