Question 472863
  <pre><font face = "Tohoma" size = 4 color = "indigo"><b> 
Hi,
Is the line through points P(1, 9) and Q(9, 6) perpendicular to the line
 through points R(-6, 0) and S(-9, 8)?
Using the point-slope formula, {{{m =(y[2] - y[1])/(x[2] - x[1])}}}
P(1, 9) and 
Q(9, 6)     m = 3/-8 = -3/8

R(-6, 0) and 
S(-9, 8)    m = -8/3 
b. No; their slopes are not opposite reciprocals. 
(their slopes are only reciprocals-same sign)