1. Find the sum of the first k terms of the following sequences for the given value of k. a. an = 3 – 3n , k = 315 b. an = 2(3)" , k = 6 2. Use polynomial fitting to find a closed formula for the...

Please answer question 1a and 1b with details on how to do it. Thank you.

Extracted text: 1. Find the sum of the first k terms of the following sequences for the given value of k. a. an = 3 – 3n , k = 315 b. an = 2(3)" , k = 6 2. Use polynomial fitting to find a closed formula for the sequence (an)n e N: -2,–1,4,13,26, ...