Math CentralQuandaries & Queries


Question from C, a parent:

These are a two part each

Can you help me determine wheter these lines are parallel, perpendiculare or neither and why?

Problem 1: y=3x+2
y=1/3x - 4

Problem 2: y=1/3x + 1/2
y=1/3 x -2



If you write the equation of a line in the form y = mx + b then the slope of the line is the number m. Two lines are parallel if they have the same slope so in your second problem the two lines are paralel since they both have the slope 1/3.

Two lies of slope m and n are perpendicular if n = -1/m. In your first problem the slopes are 3 and 1/3 so they are not perpendicular. The lines y = 3x + 2 and y = -1/3x - 4 are perpendicular.


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