Parallel lines never intersect each other, so the slopes of opposite parallel sides of a quadrilateral are equal. The correct option is a).
A quadrilateral is a polygon with four sides connected to each other The sum of all the interior angles of a quadrilateral is equal to 360 degrees.
The coordinate geometry can be used in order to prove the opposite sides of a quadrilateral are parallel.
Parallel lines never intersect each other, so the slopes of opposite parallel sides of a quadrilateral are equal.
Therefore, the correct option is (a) use the slope formula to prove the slopes of the opposite sides are the same.
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