# SOLUTION: First Question: Find the initial term of the arithmetic sequence with 10th term -1 and 20th term 7. (use initial term a0) Second Question: There are two geometric sequences w

Algebra ->  Algebra  -> Sequences-and-series -> SOLUTION: First Question: Find the initial term of the arithmetic sequence with 10th term -1 and 20th term 7. (use initial term a0) Second Question: There are two geometric sequences w      Log On

 Ad: Algebrator™ solves your algebra problems and provides step-by-step explanations! Ad: Algebra Solved!™: algebra software solves algebra homework problems with step-by-step help!

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

 Click here to see ALL problems on Sequences-and-series Question 622864: First Question: Find the initial term of the arithmetic sequence with 10th term -1 and 20th term 7. (use initial term a0) Second Question: There are two geometric sequences with 2nd term 5 and 4th term 80. What are the two possible values of the 3rd term? I truly appreciate your help!!Answer by MathTherapy(1423)   (Show Source): You can put this solution on YOUR website! Using the formula for an arithmetic sequence, we get: ----- Substituting 10 for n in formula ---- eq (i) ----- Substituting 20 for n in formula ------ eq (ii) ---- eq (i) ---- eq (ii) - 10d = - 8 ------ Subtracting eq (ii) from eq (i) d, or difference = , or Since d = , then becomes: ----- Substituting 10 for n, and for d in formula Initial term, or ========= Check ========= 10th term - 1 = - 1 (TRUE) 20th term 7 = 7 (TRUE) Send comments and “thank-yous” to “D” at MathMadEzy@aol.com