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2011-09-20 18:03:00   来源：网络资源    双击单词自动翻译

　　Fractional Exponents　　Exponents can be fractions, too. When a number or term is raised to a fractional power, it is called taking the root of that number or term. This expression can be converted into a more convenient form:

　　Or, for example, 213 5 is equal to the fifth root of 2 to the thirteenth power:

　　The　symbol is also known as the radical, and anything under the radical, in this case , is called the radicand. For a more familiar example, look at 91 2, which is the same as :

　　Fractional exponents will play a large role on SAT II Math IC, so we are just giving you a quick introduction to the topic now. Don’t worry if some of this doesn’t quite make sense now; we’ll go over roots thoroughly in the next section.　　Negative Exponents　　Seeing a negative number as a power may be a little strange the first time around. But the principle at work is simple. Any number or term raised to a negative power is equal to the reciprocal of that base raised to the opposite power. For example:

　　Or, a slightly more complicated example:

　　With that, you’ve got the four rules of special exponents. Here are some examples to firm up your knowledge:

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