Let P and Q be constants. The graphs of the lines x + 5y = 7 and 16x + Py = Q are perpendicular and intersect at the point (8,3). Enter the ordered pair (P,Q).
The point 8, 3 is not on the line x + 5y = 7
the point -8, 3 IS on the line
plug into the second equation
16(-8) + p(3) = Q
-128 + 3p = q slope has to be 5 to be perpindicular (the slope of the first line is -1/5)
16x + py = q
py = - 16x +q so -16/p = 5 p = -16/5
-128 - 16/5 (3) = q = -640/5 - 48/5 = -688/5 =Q=........
p