## Calculus with Applications (10th Edition)

$y=7.2t+11.9$
Graphing the approximately linear function, the points on the graph are (t, y(t)). Let y be in billions of dollars, t is the number of years after 2000. Given points: (1, 19.1) and (8, 69.7). Slope: $m=\displaystyle \frac{69.7-19.1}{8-1}=\frac{50.6}{7}\approx$7.22857142857$\approx 7.2$ Point-slope equation: $y-19.1=7.2(t-1)$ $y-19.1=7.2t-7.2\qquad/+19.1$ $y=7.2t+11.9$