Answer:
a) the common difference is 20
b) 
c) the common difference is -13
d) 
Step-by-step explanation:
a) what is the common difference of the sequence xn
Looking at the table, we get x_3=16, x_4=36 and x_5= 56
Deterring the common difference by subtracting x_4 from x_3 we get
36-16 =20
So, the common difference is 20
b) what is x_8? what is x_12
The formula used is: 
We know common difference d= 20, we need to find 
Using
we can find 

So, We have 
Now finding 

So, 
Now finding 

So, 
c) what is the common difference of the sequence 
Looking at the table, we get a_7=104, a_8=91 and a_9= 78
Deterring the common difference by subtracting a_7 from a_8 we get
91-104 =-13
So, the common difference is -13
d) what is a_12? what is a_15?
The formula used is: 
We know common difference d= -13, we need to find 
Using
we can find 

So, We have 
Now finding
, put n=12

So, 
Now finding
, put n=15

So, 
A student can take three subjects in 40 ways.
<u>SOLUTION:</u>
Given that, there are 4 different math courses, 5 different science courses, and 2 different history courses.
A student must take one of each, how many different ways can this be done?
Now, number ways to take math course = 4
Number of ways to take science course = 5
Number of ways to take history course = 2
So, now, total possible ways = product of possible ways for each course = 4 x 5 x 2 = 40 ways.
Hence, a student can take three subjects in 40 ways.
You should use the calculator and just plug in those numbers
What do u need the absolute value on?
C. Revising because it should be your last stage in the writing process before you publish