When you want to find the slope of the perpendicular line, all you have to do is flip the known slope upside down and make it negative. You know that [tex] y_{1} 's[/tex] slope is 3 and you know [tex] y_{2}[/tex] is perpendicular. So, just flip 3 upside down into [tex] \frac{1}{3} [/tex] and then make it negative, -[tex] \frac{1}{3} [/tex]. If you look at the coordinate grid, you can see that [tex] y_{2} [/tex] crosses the y-axis at 4. When you put those into slope-intercept form you get [tex] y_{2} [/tex] = -[tex] \frac{1}{3} [/tex]x + 4.
