Question 66055
Well for two lines to be perpendicualr they need to be opposite reciprical of eachother so just find the slope between the two lines and if they are opposite reciprical of eachother than they are perpendicular. <br>

(2, 3) and (11, 6)
slope = {{{ (y2-y1)/(x2-x1) }}}
slope = 11-2/6-3
slope = 9/3
slope = 3<br>

(2, 3) and (-3, 18)
slope = {{{ (y2-y1)/(x2-x1) }}}
slope = -3-2/18-3
slope = -5/15
slope = -1/3<br>

since the slope between (2, 3) and (11, 6) is 3 and the slope between (2, 3) and (-3, 18) is -1/3 then the sides are perpendicualr to eachother.