Calculate the sum of the first nine terms of the arithmetic progression (bn) if: b1 = -17, d = 6

univerkov | July 18, 2021 | education

Let’s find the ninth term of the progression.
b9 = b1 + 8d = – 17 + 8 * 6 = 48 – 17 = 31.

Let’s find the sum of the first nine terms.

S9 = (b1 + b9) / 2 * 9 = (- 17 + 31) / 2 * 9 = 7 * 9 = 63.

Answer: S8 = 63.

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