Westonci.ca is the premier destination for reliable answers to your questions, brought to you by a community of experts. Discover reliable solutions to your questions from a wide network of experts on our comprehensive Q&A platform. Our platform offers a seamless experience for finding reliable answers from a network of knowledgeable professionals.

If the 6th term of an arithmetic sequence is
12 and the 15th term is -15, find the first
term and the common difference.

Sagot :

Answer:

d = -3    

[tex]a_{1}[/tex] = 27

Step-by-step explanation:

You have to use the formula [tex]a_{n} = a_{1} + (n - 1)d[/tex] two times, once for the 6th term and once for the 15th term

(1)    [tex]12 = a_{1} + (6 - 1)d[/tex]          (2)    [tex]-15 = a_{1} + (15 - 1)d[/tex]

        [tex]12 = a_{1} + 5d[/tex]                         [tex]-15 = a_{1} + 14d[/tex]  Change signs and add to (1)

        [tex]15 = - a_{1} - 14d[/tex]

         27 = -9d

          d = -3                                  - 15 = [tex]a_{1}[/tex] + 14(-3)

                                                      - 15 = [tex]a_{1}[/tex] - 42

                                                          [tex]a_{1}[/tex] = 27

Thanks for stopping by. We are committed to providing the best answers for all your questions. See you again soon. We appreciate your time. Please come back anytime for the latest information and answers to your questions. Thank you for choosing Westonci.ca as your information source. We look forward to your next visit.