Question

line 1 passes through (2,2) and (5,5). line 2 passes through (3,-6) and (-5,2). Are the lines parallel or perpendicular?

Answer 1

Find the slope of the first line, that is the difference of the y’s over the difference of the x’s. This way: 2-5/2-5=-3/-3 which equals 1
Now find the slope of the second line 2-(-6)/-5-3
=8/-8
=-1
The slopes are opposite reciprocal ( you could also say that the product of the 2 slopes equals -1) therefore the lines are perpendicular.