we know that
In an Arithmetic Sequence the difference between one term and the next is a constant
where
a1 is the first term
d is the common difference between terms
n is the number of months (in this problem)
case a) Mandy
------> equation 
in this equation the first month is April
case b) Bill
-------> equation 
In this equation the first month is May
With the equation and the equation
calculate the attached table
therefore
the answer is
December
9514 1404 393
Answer:
A. 0 = −(x−6)^2+12
Step-by-step explanation:
The vertex form of a quadratic equation is ...
y = a(x -h)² +k . . . . . . for vertex (h, k) and scale factor 'a'
When the given vertex (h, k) = (6, 12) is used, we find the form of the equation to be ...
y = a(x -6)² +12
The ball will be on the ground when y = 0. Here, the vertical scale factor 'a' is -1, so the equation representing the ball being on the ground is ...
0 = -(x -6)² +12 . . . . . . matches choice A
D=Disc
13+10d=83
10d=83-13
10d=70
D=70/10
D=7
7+1=8
Maria purchased 8 CDs. Hope this helps!
