Answer:
-1,512,390
Step-by-step explanation:
Given
a1 = 15

Let us generate the first three terms of the sequence

For 

Hence the first three terms ae 15, 8, 1...
This sequence forms an arithmetic progression with;
first term a = 15
common difference d = 8 - 15 = - -8 = -7
n is the number of terms = 660 (since we are looking for the sum of the first 660 terms)
Using the formula;
![S_n = \frac{n}{2}[2a + (n-1)d]\\](https://tex.z-dn.net/?f=S_n%20%3D%20%5Cfrac%7Bn%7D%7B2%7D%5B2a%20%2B%20%28n-1%29d%5D%5C%5C)
Substitute the given values;
![S_{660} = \frac{660}{2}[2(15) + (660-1)(-7)]\\S_{660} = 330[30 + (659)(-7)]\\S_{660} = 330[30 -4613]\\S_{660} = 330[-4583]\\S_{660} = -1,512,390](https://tex.z-dn.net/?f=S_%7B660%7D%20%3D%20%5Cfrac%7B660%7D%7B2%7D%5B2%2815%29%20%2B%20%28660-1%29%28-7%29%5D%5C%5CS_%7B660%7D%20%3D%20330%5B30%20%2B%20%28659%29%28-7%29%5D%5C%5CS_%7B660%7D%20%3D%20330%5B30%20-4613%5D%5C%5CS_%7B660%7D%20%3D%20330%5B-4583%5D%5C%5CS_%7B660%7D%20%3D%20-1%2C512%2C390)
Hence the sum of the first 660 terms of the sequence is -1,512,390
What is the system? (Is there supposed to be an image?)
Answer:
12
Step-by-step explanation:
Given :
Male Female Total
Registered 60
Non registered 40
Total 20 80
Solution :
N= 100
Formula of expected frequency = 
= expected frequency for the ith row/jth columm.
= total in the ith row
= total in the jth column
N = table grand total.
So, using formula 









![E_{22]=\frac{80 \times 40}{100}](https://tex.z-dn.net/?f=E_%7B22%5D%3D%5Cfrac%7B80%20%5Ctimes%2040%7D%7B100%7D)

Expected frequency table
Male Female Total
Registered 12 48 60
Non registered 8 32 40
Total 20 80
So, the expected frequency for males who are registered voters are 