Chapter 11 - 11.2 - Arithmetic Sequences and Partial Sums - 11.2 Exercises - Page 788: 79

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The nth term of an arithmetic sequence can be obtained by the following formula: $a_n=a_1+(n-1)d$, where $a_1$ is the first term and $d$ is the common difference. If you know the first two terms, then apart from knowing the first term, you can also determine the common difference by subtracting the first term from the second one. Then you will have a formula for the nth term. Thus the statement is true.