分条件可知：formula_175，formula_176是formula_177的极大值点；formula_178，formula_176是formula_177的极小值点；formula_181，formula_176是formula_177的拐点。formula_184可知：formula_185，formula_173的驻点为极大值点；formula_187，formula_173的驻点为极小值点；formula_189，formula_173的驻点为拐点。