Question

sum of the first 5 terms is 320 and the sum of the next five term is 395 find the 3rd term and 8th term , find the sum of first 10 terms​

Answer 1

Step-by-step explanation:

Sum of first five terms=

2

5

(2a+4d) and

Sum of first ten terms =5(2a+9d)

⟹

2

5

(2a+4d)=5(2a+9d)

⟹a+2d=2a+9d

⟹d=

7

−a

So, either the first term is negative or the common difference is negative.

Hence, option C is correct.