Question 1158788
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The formulas are just given to you under these links


https://www.algebra.com/algebra/homework/Sequences-and-series/Sequences-and-series.faq.question.1158774.html


         and


https://www.algebra.com/algebra/homework/Sequences-and-series/Sequences-and-series.faq.question.1158775.html



Use them.   Substitute the given values into the formulas and complete the job on your own.


Please  DO  NOT  EXPECT  the tutors will do your job instead of you.


<H3>Making calculations is the students' honor duty and a privilege (!)</H3>