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

$a.\quad U=10n+137$ $b.\quad$257 million, exact value
a. $U=4(2n+32)+2(n+\displaystyle \frac{9}{2})\qquad$... distribute $U=(8n+128)+(2n+9)\qquad$... get rid of parentheses $U=8n+128+2n+9\qquad$...rearrange and group like terms $U=(8n+2n)+(128+9)$ $U=10n+137$ b. In 2012 (12 years after 2000), $n=12$. Substituting, $U=10(12)+137$ $=120+137$ $=257$ (million) The same value is shown on the graph, so the model gives the exact value for 2012.