Let u(x, y) be the 2-variable function u(x, y) = (x + 2)y − exp(x + y). (a) Find the partial derivatives ux, uy, uxx, uyy, and show that uxy = uyx.
(b) Show that u has a stationary point for y = 1. Determine the corresponding value
of x and the character of the stationary point.

Lian is deciding which of two gyms to join. each gym charges a monthly rate plus a one-time membership fee. lian correctly wrote and solved a system of linear equations by substitution to compare the costs of the memberships. in her work, she substituted an expression for one variable and solved for the other. this resulted in the equation 75 = 75. what can lian conclude? one gym charges $75 per month. each gym charges $75 per month both gyms charge the same monthly rate and the same membership fee. both gyms charge the same monthly rate, but not the same membership fee.