First knowing that the slope intercept form is
`y = mx+b` where m is the slope (rise over run) and b is the y intercept (x=0).
Pick points a and b that will be easy to use, such as 0, 2 and 6, 5.
The slope is 3/6 and the y intercept is 2 so the first equation is
`y = (1/2)x + 2`
Point c must be off of the line in question such as 0,0
Using the point slope formula and the fact that the product of the slopes of perpendicular lines is -1, you can find the other equation.
The slope must be the opposite of the reciprocal of the first slope in order to get a product of -1 so the second slope is `-2` .
The point slope formula is
`y-y' = m(x-x')`
Substituting the point c for x' and y' you get
`y-0 = (-2)(x-0)` or ` <strong>y =-2x</strong> `
You can see now why I chose 0.0. You can choose any other point that is not on the first line and solve for y, it just takes more steps.