Question 851446
SLOPE FORMULA
Two points (r,s) and (u,v) in a plane have slope {{{(v-s)/(u-r)}}}.


Lines with equal slopes are parallel.  Opposite sides of a parallelogram are parallel; this occurs for both pair of opposite sides of a parallelogram.  This also means that opposite sides of a parallelogram have the same slope.


The instruction, "Use the slope formula", means find the slope for AB, BC, CD, and DA.  Now you can answer the question.