The sum of the first twelve terms of an arithmetic sequence of real numbers is 60. The first term is -6. What is the sum of the first twenty terms?
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Originally Posted by Espionage The sum of the first twelve terms of an arithmetic sequence of real numbers is 60. The first term is -6. What is the sum of the first twenty terms? Suppose that is the sum of the first n terms and d is the common difference then where is the first term.
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