Slope Formula and how to use it.

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Using slope formula to prove parallelograms is important to exhibit the definition of a parallelogram. You will need to find the slope of all 4 sides to prove that they are parallel. the slope formula is:

Let's use this example: A(2,5) B(3,2) C(10,1) D(9,4)

I'll start by finding the slope of line AB

So this makes sense. If you follow point A to point B, you have to shift down the y axis by 3, and move over to the x axis by 1. It is negative because the slope is declining (like think about sliding down a slope when skiing) if it were positive you would be ascending from point A (like hiking up a hill)

QUESTION: Find the Slope of DC, AD and BC to prove all sides are parallel to the opposite side