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The first term of an arithmetic sequence is -8. Find the 20th term if the sum of the first 20 terms is 790.

 Jul 2, 2020
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[- 8 + L]/2 * 20 = 790, solve for L
[-8 + L] * 10 = 790
[-8 + L] = 79
L =79+8 = 87 - The last and 20th term.

 Jul 2, 2020

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