SOLUTION: Find a1 of arithmetic sequence from given information. a7=-45 a15=-77

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 Algebra: Sequences of numbers, series and how to sum them Solvers Lessons Answers archive Quiz In Depth

 Question 39435: Find a1 of arithmetic sequence from given information. a7=-45 a15=-77Answer by AnlytcPhil(1278)   (Show Source): You can put this solution on YOUR website!```Find a1 of arithmetic sequence from given information. a7 = -45 a15 = -77 Use the formula: an = a1 + (n-1)d a7 = a1 + (7-1)d -45 = a1 + 6d a15 = a1 + (15-1)d -77 = a1 + 14d So you have this system of equations: -45 = a1 + 6d -77 = a1 + 14d Can you solve that system of equations? If not post again. a1 = -21, d = -4 Edwin AnlytcPhil@aol.com ```