## Precalculus (10th Edition)

$y = \frac{1}{2}x + \frac{5}{2}$
First compute the slope of the line with $(x_1, y_1) = (1, 3)$ and $(x_2, y_2) = (-1, 2)$. Slope: $m = \dfrac{y_2-y_1}{x_2-x_1}\\ m=\dfrac{2-3}{-1-1}\\ m=\dfrac{-1}{-2}\\ m=\dfrac{1}{2}$ Use the point $(1, 3)$ and the slope $\frac{1}{2}$ to get the point-slope form of the equation of the line, then isolate $y$ to obtain the slope-intercept form: $y - 3 = \frac{1}{2}(x - 1)\\ y - 3 + 3 = \frac{1}{2}(x - 1) + 3\\ y = \frac{1}{2}x - \frac{1}{2} + 3\\ y = \frac{1}{2}x + 3 - \frac{1}{2}\\ y = \frac{1}{2}x + \frac{5}{2}$