Follow these steps to prove the given quadrilateral is a parallelogram.

✓ 1. Determine the slope of AB: −4/3 0 4/3

✓ 2. Determine the slope of DC: 0 3/4 4/3

✓ 3. Determine the length of AB: 5 16 25

✓ 4. Determine the length of DC: 5 16 25

✓ 5. Because a pair of opposite sides is both parallel and congruent, ABCD is a parallelogram.