SOLUTION: Which of the folowing are the pair of equations whose graphs are not perpendicular? A. 2x-8y=9 12x-3y=7 B.3x+6y=8 y=2x-8 C.y=x-7 x+y=3 D. 2y=3x+5 2x+3y=4

Algebra ->  Algebra  -> Graphs -> SOLUTION: Which of the folowing are the pair of equations whose graphs are not perpendicular? A. 2x-8y=9 12x-3y=7 B.3x+6y=8 y=2x-8 C.y=x-7 x+y=3 D. 2y=3x+5 2x+3y=4      Log On

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Question 83167: Which of the folowing are the pair of equations whose graphs are not perpendicular?
A. 2x-8y=9
12x-3y=7
B.3x+6y=8
y=2x-8
C.y=x-7
x+y=3
D. 2y=3x+5
2x+3y=4
Answer by Mona27(45) About Me  (Show Source):
You can put this solution on YOUR website!
It's the first one (A)
That's because the product of the gradients (slopes) of two perpendicular lines must be -1.
In the first case:
the gradient of the first line = 2%2F8=1%2F4
and the gradient of the second line = 12%2F3=4
since both gradients are positive then they cannot give a product of -1, and therefore are not perpendicular.