If two lines have slopes

m and

n , respectively, are they perpendicular?

1.

m*n=-12.

m=-nI have an issue in OE when explaining the statement 2. From OE shown below one can still answer the question that whether m & n are perpendicular.

I think in OE there should be two examples. First an example of two lines

y= x+10 &

y=-x+10, here you can see that the lines are parallel as the product of their slope is

-1. In second example we can quote

y=10x &

y=-10x. Now its make more sense that statement 2 is insufficient.

OE:

Statement (2) by itself is insufficient. We only know that the lines have reciprocal slopes. For example line

y=10x and

y=-10x , are mirror reflections of each other on the x axis, but not perpendicular.

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