SOLUTION: 3x-6y= -15 and 18x+9y=20 are these lines parallel, perpendicular, or neither?

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Question 370122: 3x-6y= -15 and 18x+9y=20 are these lines parallel, perpendicular, or neither?
Answer by robertb(5830) About Me  (Show Source):
You can put this solution on YOUR website!
The first is the same as x-2y = -5, the second, the same as 2x + y = 20/9. Two lines of the form ax + by = c and bx - ay = d are perpendicular. Since these two lines are such, then they are perpendicular.