Question 78573
we need to find the slopes of these two lines to prove if they are perpendicular. Thus:
(6-3)/(11-2)=3/9=1/3 for the slope through the first set of points.
the formula for this line is:
3=2/3+b
b=3-2/3
b=7/3 or
y=x/3+7/3 (red line)
(18-3)/(-3-2)=15/-5=-3 this slope is the negative reciprical of the first slope.
3=-3*2+b
3=-6+b
b=3+6
b=9
y=-3x+9 (green line)
Therefore these lines are perpendicular as proven by the following graph-
{{{ graph( 300, 300, -10, 10, -10, 10, y = x/3 +7/3, y = -3x +9) }}} (graph 300x300 pixels, x from -10 to 10, y from -10 to 10, of TWO functions y = x/3 +7/3 and y = -3x +9).