文档介绍：小亮 GRE数学总结
GRE数学考试中的主要符号
+
plus ;positive
-
minus ;negative
×
multiplied by ;times
÷
divided by
=
Equals
≈
approximately equals
≠
not equal to
<
less than
>
greater than
≤
equal to or less than
≥
equal to or greater than o
( )
round brackets ;parentheses
[ ]
square brackets
{ }
Braces
∈
is a member of the set
⊂
is a subset of
∽
similar to
≌
congruent to
*
denotes an operation
∴
Therefore
∵
Because
∶
ratio sign, divided by, is to
∷
equals, as(proportion)
square root of
cube root of
∥
parallel to
⊥
perpendicular to, at right angles with
∠
Angle
∟
right angle
º
Degree
′
Minute
″
Second
⊙
Circle
A⁀B
arc AB
e
the base of natural logarithms,
x!
factorial x, x(x-1)(x-2)---1
lognx
log x to the base n
π
Pi
lnx
log x to the base e(natural logarithm)
lgx
log x to the base mon logarithm)
|x|
the absolute value of x
数的概念和特性
*几个GRE最常用的概念:
偶数(even number):能被2整除的整数;
奇数(odd number):不能被2整除的数;
质数(prime number):大于1的整数,除了1和它本身外,不能被其他正整数所整除的,称为质数。也叫素数;(学过数论的同学请注意,这里的质数概念不同于数论中的概念,GRE里的质数不包括负整数)
倒数(reciprocal):一个不为零的数为x,则它的倒数为1/x。
等差数列
GRE数学中绝大部分是等差数列,,形式主要为应用题。题目会说三年稳步增长第一年的产量是x,第三年的产量是y,问你的二年的产量。
数理统计
*众数(mode) 
一组数中出现频率最高的一个或几个数。
例:mode of 1,1,1,2,3,0,0,0,5 is 1 and 0。
*值域(range)
一组数中最大和最小数之差。
例:range of 1,1,2,3,5 is 5-1=4
*平均数(mean) 算术平均数(arithmetic mean)
*几何平均数(geometric mean)
n个数之积