The slope of a line is given by the formula:
Where m is the slope, (x1,y1) and (x2,y2) are the coordinates of two points on the line.
In the first line we can identify the next two points: (0,0) and (2,1).
The slope of this line is:
In the second line, the two points that we can identify are: (0,4) and (2,1).
The slope is then:
In order to know if they are perpendicular, we need to know that two perpendicular lines have slopes that are negative reciprocal to each other, it means:
We need to check if this is true with the two slopes we have, then :
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