SOLUTION: Let line A be the graph of 5x + 8y = -9. Line B is perpendicular to line A and passes through the point (10,10). If line B is the graph of the equation y=mx +b, then find m+b.

Algebra ->  Graphs -> SOLUTION: Let line A be the graph of 5x + 8y = -9. Line B is perpendicular to line A and passes through the point (10,10). If line B is the graph of the equation y=mx +b, then find m+b.      Log On


   

Question 1069446: Let line A be the graph of 5x + 8y = -9. Line B is perpendicular to line A and passes through the point (10,10). If line B is the graph of the equation y=mx +b, then find m+b.
Answer by Fombitz(32388) About Me  (Show Source):
You can put this solution on YOUR website!
5x%2B8y=-9
8y=-5x-9
y=-%285%2F8%29x-9%2F8
Perpendicular lines have slopes that are negative reciprocals,
-%285%2F8%29m%5B2%5D=-1
m%5B2%5D=8%2F5
So then using the point-slope form of a line,
y-10=%288%2F5%29%28x-10%29
y-10=%288%2F5%29x-16
y=%288%2F5%29x-6
So,
m%2Bb=8%2F5-6=8%2F5-30%2F5=-22%2F5