omplete the proof to show that abcd is a parallelogram. on a coordinate plane, quadrilateral a b c d is shown. point a is at (negative 2, negative 2), point b is at (negative 3, 4), point c is at (2, 2), and point d is at (3, negative 4). the slope of line segment b c is startfraction 4 minus 2 over negative 3 minus 2 endfraction