Mathematics, 29.06.2019 22:00 discolldiane7351
The sum of the first n terms of an a. p. is 2n and the sum of the first 2n terms is n. find the sum of the first 4n terms.
Answers: 1
![S_n=\frac{n}{2}[2a+(n-1)d]](/tpl/images/0032/5459/b603c.png)
![\frac{n}{2}[2a+(n-1)d]=2n](/tpl/images/0032/5459/6b2b7.png)
..... (1)![\frac{2n}{2}[2a+(2n-1)d]=n](/tpl/images/0032/5459/8fffa.png)
..... (2)
![S_{4n}=\frac{4n}{2}[2a+(4n-1)d]](/tpl/images/0032/5459/2df69.png)
![S_{4n}=2n[2a+(4n-1)d]](/tpl/images/0032/5459/13810.png)
![S_{4n}=2n[2(\frac{1}{2}(7-\frac{3}{n}))+(4n-1)(-\frac{3}{n})]](/tpl/images/0032/5459/ab54b.png)
![S_{4n}=2n[7-\frac{3}{n}-12+\frac{3}{n}]](/tpl/images/0032/5459/8d596.png)
![S_{4n}=2n[-5]](/tpl/images/0032/5459/a584a.png)
Other questions on the subject: Mathematics
Mathematics, 21.06.2019 19:20, TrudnEli1217
Which number completes the system of linear inequalities represented by the graph? y> 2x – 2 and x + 4y 2 et 2 3 4
Answers: 3
You know the right answer?
The sum of the first n terms of an a. p. is 2n and the sum of the first 2n terms is n. find the sum...
Questions in other subjects:
Mathematics, 30.07.2019 06:00
Physics, 30.07.2019 06:00
History, 30.07.2019 06:00
Mathematics, 30.07.2019 06:00
History, 30.07.2019 06:00
History, 30.07.2019 06:00
