SOLUTION: For what value of a is the graph of 5y = ax + 7 perpendicular to the graph of by + 3x = 12?

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Question 310277: For what value of a is the graph of 5y = ax + 7 perpendicular to the
graph of by + 3x = 12?
Answer by Fombitz(32388) About Me  (Show Source):
You can put this solution on YOUR website!
Put both lines in slope-intercept form, y=mx%2Bb
5y=ax%2B7
y=%28a%2F5%29x%2B7%2F5
.
.
.
by%2B3x=12
by=-3x%2B12
y=-%283%2Fb%29x%2B12%2Fb
.
.
.
Perpendicular lines have slopes that are negative reciprocals,
m1%2Am2=-1
%28a%2F5%29%28-%283%2Fb%29%29=-1
%283a%29%2F%285b%29=1
3a=5b
highlight_green%28a=%285%2F3%29b%29