GRE数学考试在新GRE考试当中增加了一些难度，但是考生也不要太紧张，只要把一些GRE数学基本概念掌握好，解题时就一定能轻松应对。

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　　一元二次方程

　　ax2+bx+c=o

　　x12=[-b±(b2-4ac1/2)]/2a

　　描述统计Descriptive statistics

　　mode 众数

　　一组数中出现频率最高的数

　　极差range

　　一组数中最大值与最小值之间的差值

　　平均数mean

　　算术平均arithmetic mean

　　几何平均geometric mean

　　例题.The circumference of a rectangle is 20

　　A.The greatest area of the rectangle

　　B.25

　　中位数median

　　中位数的寻找方法：

　　1.将所有n个数字按着从大到小或者从小到大排列;

　　2.如果n=奇，整个序列中位于中间位置的数就是中位数;如果n=偶，中间两个数的算术平均即是中位数。

　　例题.If the arithmetic mean of a, b, c, 3 and 5 is 6, which of the following must be true?

　　1.The median of the five numbers cannot be 3

　　2.At least one of a, b and c is greater than 7

　　3.The range of the five numbers is 2 or more

　　A.1 only

　　B.2 only

　　C.3 only

　　D.1 and 3

　　E.2 and 3

　　例题.A group of students were tested on data-entry skills, and the number of errors they made and the percent of students making x errors were recorded as follows.