新GRE数学复习要点之Substitution

　　Substitution

　　Substitution is a method where one or more variables in an expression is replaced by numbers or another set of variables.To evaluate an expression specific numbers are used as substitute. To express in terms of another set of variables, variables are replaced by the new set of variables

　　Example:

　　If x=3, then 2x2+4x+1 can be evaluated by substituting 3 for x.

　　Replacing all x by 3, we get 2*32+4*3+1=31.

　　If x=2+y, then x2-3 can be expressed in terms of y by replacing all x by (2+y):(2+y)2-3=y2+4y+1.

　　Remember:

　　Do not forget to replace all occurrences of the variable.

　　After substitution the variable does not appear anywhere in the expression.

　　由于美国数学基础教育的.难度增加导致数学考试越来越难，但新gre数学复习考点都是高中时候学到的知识点，考生不要过于紧张，把基本概念弄明白，再记住一些新版gre数学必备的词汇，那么相信新版gre数学应该没有问题。

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