The nth term of an Arithmetic Sequence
The nth term of an arithmetic sequence can be found using this formula, shown in Figure 1.
In this formula, a is the first term, n is the term number and d is the common difference.
Consider this sequence
2, 5, 8, 11,...
Here the first term is 2 and the common difference is 5-2, or 3.
or, simplified, 3n-1.
The Sum of an Arithmetic Sequence
The sum of and arithmetic sequence can be found using this formula.
In this case, n is the number of numbers being summed.
Consider the previous sequence.
If we had to sum the first ten numbers in this sequence, we would put the values of n, a and d into the formula.
Try these questions.
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