Given:
Line a passes through (2, 10) and (4, 13).
Line b passes through (4, 9) and (6, 12).
Line c passes through (2, 10) and (4, 9).
To find:
Which of the lines, if any are perpendicular.
Solution:
If a line passes through two points, then the slope of line is

Line a passes through (2, 10) and (4, 13). So, slope of this line is

Line b passes through (4, 9) and (6, 12). So, slope of this line is

Line c passes through (2, 10) and (4,9). So, slope of this line is

Product of slopes of to perpendicular lines is -1.



Therefore, any of these lines are not perpendicular to each other.