SOLUTION: Which of the following statements are true ? a. the lines y = 2x - 5, y = ax + 3 are perpendicular when a = -1/2 b. the lines y = 4x + 3, y = ax + 2 are

Question 299886: Which of the following statements are true ?
a. the lines
y = 2x - 5, y = ax + 3
are perpendicular when a = -1/2
b. the lines
y = 4x + 3, y = ax + 2
are parallel when a = 4

c. a vertical line has undefined slope.
I don't understand how to solve this problem. Please help.
Answer by Alan3354(69443) (Show Source): You can put this solution on YOUR website!
Which of the following statements are true ?
a. the lines
y = 2x - 5, y = ax + 3
are perpendicular when a = -1/2
-----------------
The slope of the 1st eqn is +2. The slope of any line perpendicular is the negative inverse, = -1/2.
So it's true.
----------------
b. the lines
y = 4x + 3, y = ax + 2
are parallel when a = 4
The slope of the 1st eqn is +4. All lines parallel will have the same slope, so it's true.
------------------------------
c. a vertical line has undefined slope.
True. Parallel to the y-axis is often referred to as vertical.
Slope = change in y/change in x
The change in x = 0 --> undefined.
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