求翻译：关于理科的复习与练习，首先是公式，对公式要非常熟悉，公式中每个字母的含义，公式的推导，公式的使用对象，这些是很重要的，从现在开始，把各科所有公式分类并用一个本子整理一遍，做题的时候强化这些公式的记忆与使用，做到看到题目就知道要用到什么公式，以及清楚公式中字母对应的数字，在平时做练习题时，就要要求自己写出题目已知什么，未知什么，求什么，相关公式，这些都清楚了在解答。考试时当然不用写出来，但自己必须清楚。是什么意思？

On Science of review and exercises, first is formula, on formula to very familiar, formula in the each letters of meaning, formula of derivation, formula of using object, these is is important of, from now began, to all branch all formula classification and a book finishing a again, do questions of when strengthening these formula of memory and using, do see topic on know to with to what formula, and clearly formula in the letters corresponds of digital, in usually do exercises Shi, will requirements own writes topic known what, unknown what, seeking what, related formula, these are clearly has in answers. Examination of course not written, but they must make it clear.