Answer: Choice C
Perpendicular because the slopes are negative reciprocals of each other.
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Explanation:
Use the slope formula to find the slope of line AB
m = (y2-y1)/(x2-x1)
m = (-1-(-2))/(4-8)
m = (-1+2)/(4-8)
m = 1/(-4)
m = -1/4
The slope of line AB is -1/4
Repeat those steps for line CD
m = (y2-y1)/(x2-x1)
m = (-9-11)/(-2-3)
m = (-20)/(-5)
m = 4
The slope of line CD is 4
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The slopes of AB and CD are -1/4 and 4 respectively.
We can see that the two slopes are negative reciprocals of each other. Meaning that one slope will have us flip the fraction and the sign to form the other slope, and vice versa. Therefore, the two lines are perpendicular.
One useful property is that perpendicular slopes like this multiply to -1
(-1/4)*(4) = -1
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Side note: If the slopes were equal, then the lines would be parallel (assuming the two lines have different y intercepts).
