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

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.