Question

sum of first 15 terms of an arithmetic sequence is 720 and sum of first 5 terms is 100. a)find 8th term. b)find 13th term. c)find common difference​

Answer 1

Step-by-step explanation:

Refer to the attachment..

Answer 2

$\huge\fbox \red{A}\fbox \green{N}\fbox \purple{S}\fbox \orange{W}\fbox \red{E}\fbox \blue{R}$

Let a be the 1st term and d be the common difference of an A.P. , accordingly :-

S15 = (15/2).[ 2a +(15–1).d]. = 480

or, (15/2).2.(a+7d) = 480.

or a. + 7.d = 32.

or, a + (8–1).d = 32.

or, T8 = 32. Answer