Carmen is given a parallelogram and is trying to prove that the opposite angles of a parallelogram are congruent. She draws a parallelogram and a diagonal as
shown.

answer: evaluate the objective function at each vertex to determine which - and -values, if any, maximize or minimize the function. example: find the minimum value and maximum value of the objective function f ( x , y ) = 4 x + 5 y , subject to the following constraints