课时一　代数式代数式是用基本运算符号 ,把数或表示数的字母连结而成的式子 .特殊地 ,单独一个数或者表示数的字母也是代数式 .要注意字母表示数时 ,同一问题中 ,同一个字母应表示同一个数 ,不同的数要用不同的字母表示 .列代数式与求代数式的值 ,是本课中两个重要内容 .基础 Class hour algebraic algebraic expressions are basic equations that combine numbers or letters that represent numbers. In particular, a single number or letter that represents a number is also algebraic. Note that when a letter represents a number, the same question, One letter should represent the same number, and different numbers must be represented by different letters. The values ​​of column algebraic expression and algebraic expression are two important contents of this lesson.