SOLUTION: For what value of a are the equations 3x+12y=-6 and 6y=ax+9 perpendicular? A. 26 B. 24 C. -12 D. -1.5

Algebra ->  Linear-equations -> SOLUTION: For what value of a are the equations 3x+12y=-6 and 6y=ax+9 perpendicular? A. 26 B. 24 C. -12 D. -1.5      Log On


   

Question 690256: For what value of a are the equations 3x+12y=-6 and 6y=ax+9 perpendicular?
A. 26
B. 24
C. -12
D. -1.5
Answer by ReadingBoosters(3246) About Me  (Show Source):
You can put this solution on YOUR website!
3x+12y= -6
solve for y
12y = -3x - 6
y = %28-3%2F12%29x+-+6%2F12
...
y = %28-1%2F4%29x+-+1%2F2
...
slope is -1%2F4, a perpendicular line will have a slope of negative inverse.
...
A perpendicular line will have a slope of 4
...
6y = ax+9
y = %28a%2F6%29x+%2B+9%2F6
a%2F6+=+4 ==> multiply both sides by 6
a = 24
...
highlight_green%28Choice_B%29
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