Which method would prove the quadrilateral is a parallelogram? a. both pairs of opposite sides are parallel. b. both pairs of opposite sides are congruent. c. one pair of opposite sides is both parallel and congruent. d. both pairs of opposite angles are congruent.

Suppose that the price p, in dollars, and the number of sales, x, of a certain item follow the equation 4 p plus 4 x plus 2 pxequals56. suppose also that p and x are both functions of time, measured in days. find the rate at which x is changing when xequals2, pequals6, and startfraction dp over dt endfraction equals1.5.