题目

­If x is positive and the distance between -7 and 0 is equal to the distance between x and 0, what is the value of x?

选项

A.

1

B.

3

C.

5

D.

7

E.

9

解析

如果\(x\)是正数,且\(-7\)与\(0\)之间的距离等于\(x\)与\(0\)之间的距离,那么\(x\)的值是多少? 在数轴上,\(-7\)与\(0\)之间的距离为\(\vert -7 - 0\vert=\vert-7\vert = 7\)。 因为\(x\)是正数且\(x\)与\(0\)之间的距离等于\(-7\)与\(0\)之间的距离,根据绝对值的定义,可知\(\vert x - 0\vert=\vert x\vert = x\)(因为\(x>0\)),且\(x = 7\) 所以本题答案为D。
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