Question

Write an expression for the eighth partial sum of the series using summation notation

Answer 1

Answer:

option B

Step-by-step explanation:

9/10 + 6/5 + 3/2...........

We find the difference between the terms

$\frac{6}{5} - \frac{9}{10}$

$\frac{12}{10} - \frac{9}{10} = \frac{3}{10}$

We will get the same difference when we subtract consecutive terms.

so , d= 3/10, a= 9/10

we find the formula for nth term

a_n = a+(n-1) d

$a_n = \frac{9}{10} + (n-1)\frac{3}{10}$

$a_n = \frac{9}{10} +\frac{3}{10}n-\frac{3}{10}$

$a_n = \frac{6}{10} +\frac{3}{10}n$

$a_n = \frac{3}{5} +\frac{3}{10}n$

we need to find eighth partial sum so we  take n=1 to 8

sum of 8 terms ($\frac{3}{5} +\frac{3}{10}n$)

So option B is correct