Suppose that {{MATH_646}} is continuous on an open interval and that {{MATH_647}} for some value of {{MATH_648}} in that interval. {{CMD_649}} {{CMD_650}} If {{MATH_651}}, then {{MATH_652}} has a local maximum at {{MATH_653}}. {{CMD_654}} If {{MATH_655}}, then {{MATH_656}} has a local minimum at {{MATH_657}}. {{CMD_658}} If {{MATH_659}}, then the test is inconclusive. In this case, {{MATH_660}} may or may not have a local extremum at {{MATH_661}}. {{CMD_662}} {{CMD_663}}