Answer:
Step-by-step explanation:

Just take n=1,2,3,4,5 respectively to find out the first 5 terms.
First 5 terms = 4,3,2.25,1.69 respectively.
For the 5th partial sum, just add the first 5 terms.
5th partial sum = 10.34
....
First 4 terms : 5,8,11,14 respectively.
Now you need to find the other next 4 terms to find out the 8th partial sum.
17,20,23,26
8th partial sum = 124
Hope this helps:)
Answer:
15
Step-by-step explanation:
Pls find attached picture
Your answer is 18 :)
work:
pi(2)d
pi(72)
72/2=36=d
2r=d
36/2=18=r