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Explanation:
Let's find the slope of line AB
m = (y2-y1)/(x2-x1)
m = (2-7)/(-6-4)
m = (-5)/(-10)
m = 1/2
The slope of line AB is 1/2
To get the slope of BC, we flip the fraction and the sign to get the perpendicular slope
1/2 becomes -2/1 or simply -2
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Slope of AB = 1/2
Slope of BC = -2
Notice how the two perpendicular slopes multiply to -1.
We know they are perpendicular because the four angles of any rectangle are always 90 degrees each.
