您传递一个用作谓词的公式，检查它是否是一个有效的元素规则。
You pass a formula used as a predicate to see if it is a valid rule for the element.
就像大多数八年级的代数学生一样，一些投资者只是简单地记了几个公式或者规则就觉得自己天下无敌了，但很多时候他们并不知道自己到底在干什么。
Like most eighth - grade algebra students, some investors memorize a few formulas or rules and superficially appear competent but do not really understand what they are doing.
公式语言有严格的语法规则和对语句结构的要求。
Formal languages tend to have strict syntax rules that govern the structure of statements.
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