APPM 2350 Midterm: appm2350spring2018exam2_sol
Document Summary
Instructions: electronic devices, notes, books, and crib sheets are not permitted. Write your (1) name, (2) instructor"s name, and (3) lecture number on the front of your bluebook. Note that a correct answer with incorrect, or insu cient supporting work may receive no credit, while an incorrect answer with relevant work may receive partial credit. Solution: we rst calculate hx = x( 40y2 + 80) and hy = y( 40x2 + 80). There are no locations for which hx and/or hy are unde ned. We then look for critical points (cps) associated with hx = 0 and hy = 0 (simultaneously). D = hxxhyy h2 xy = ( 40y2 + 80)( 40x2 + 80) ( 80xy)2 . We can now evaluate d at each of the cps to get d|p0 = 802 > 0, however d evaluated at points p1 through p4 have the common value d = (160)2 < 0.
