我国著名数学家华罗庚曾经说过:“要善于‘退’,足够地‘退’,‘退’到原始而又不失重要性的地方,这是学好数学的一个诀窍.”对一个数学问题的研究,我们可采用:从研究全体退到研究部分;从研究复杂退到研究简单,从研究一般退而研究特殊,实现退中求进,将从部分、简单、特殊背景下研究所得结论推广到全体、复杂、 The famous Chinese mathematician Hua Luogeng once once said: “To be good at ’retreat’, enough to ’retreat’, ’retreat’ to the original but without losing importance, this is a know-how for learning mathematics.” For a mathematical problem Research, we can use: from the study of the whole regression to the research part; from the study of complex regression to the study is simple, from the general study of the study and back to the special, to achieve retreat from the progress, the results will be generalized from the part, simple, special background All, complicated,