Find an equation for line with y-intercept 3 
that is perpendicular to the line 



Compare that to the "slope y-intercept" form



and you see that the slope is  

Now we use the rule:

If a line has slope  then 
1. A line parallel to it will ALSO have slope 
2. A line perpendicular to it will have slope 
(Note: if the slope is a whole number and
not a fraction, write it over 1, so it will be
in the form )

A line perpendicular to a line with slope  will
therefore by the 2nd rule above have slope 

Now all we have to do is use the slope y-intercept form



this time with  and , so we have



If , Find . 

First find  by replacing  by 



Now find  by replacing  by 



So  =  =  =

 =  =  =



Edwin