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生学初学代数,往往错误地认为,字母 X 代表正数,-X代表负数。教师虽然讲了多次,但错误仍然不断出现。究其缘故,多因教师在讲字母 X 表示数时,举的例子往往是一些正数,很少举出 X 表示负数的例子,没有注意引导学生深入理解X 可以表示任意的有理数。致使有的学生说:我认为 X 是正数,因为 X 前面有正号,-X 是负数,因
Students begin to learn algebra and often mistakenly believe that the letter X represents a positive number and -X represents a negative number. Although teachers talked about many times, mistakes still appear constantly. For the sake of reason, because teachers often use the letter X to represent numbers, the examples cited are often positive numbers. They rarely give examples in which X represents negative numbers, and do not pay attention to instruct students to further understand that X can represent arbitrary rational numbers. As a result, some students said: I think X is a positive number, because X has a positive sign in front of it, and -X is a negative number.