1. The sum of the first 10 terms of an arithmetic sequence is 530. what is the first term if the last term is 80? what is the common difference.

2. The third term of an arithmetic sequence is -12 and the seventh term is 8. What is the sum of the first 10 terms?

3. Find the sum of the first 25 multiples of 8.



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1.) a₁ = 26   Common difference = 6

2.) Sum = 5

3.)  2,600

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