Question 510930
This is a trick question.
The line y=3 means that for all x, from -infinity to +infinity, will have y=3.
There is no change in y, so the slope = 0.
y = 3 can be shown as y = 0x + 3.
The line y=3 is a horizontal line.
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So, the line perpendicular to it will be a vertical line.
Of course, a vertical line's slope is undefined because there is no change in x for all values or 'y'.
Dividing by 0 is undefined so the slope is undefined, not 0.
To define a vertical line that goes through the point (5,1), simply state x=5.
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Done.