7. (10) Let U CR” be open, c EU, f:U + R, and suppose f'(c; u) exists for all u ER". Show that either f'(c; u) = 0 for a
Posted: Thu May 12, 2022 6:39 am
7. (10) Let U CR” be open, c EU, f:U + R, and suppose f'(c; u) exists for all u ER". Show that either f'(c; u) = 0 for all u € R" or 3u1, U2 E R" such that f'(c; u1) > 0 and f'(c; u2) <0.