Answer:
Step-by-step explanation:
Equation
L = a + (n - 1)*d
Givens
L = 55
a = 13
n =8
Solution
55 = 13 + (8 - 1)*d Combine
55 = 13 + 7d Subtract 13 from both sides
55 - 13 = 7d
42 = 7d Divide by 7
d = 6
Answer: 21
Step-by-step explanation:
84 divided by 4 = 21 since grabielle is 21, and then mikhail is gonna be 3 times more so it’s gonna be 63
Answer:
<em>0 $20 bills and 10 $5 bills</em>
<em>1 $20 bills and 6 $5 bills</em>
<em>2 $20 bills and 2 $5 bills</em>
Step-by-step explanation:
<u>Equations</u>
Let's set:
x=number of $5 bills
y=number of $20 bills
The total amount Sara has is given by
5x+20y
And we know it's equal to $50, thus:
5x+20y=50
Dividing by 5
x+4y=10
We would need another condition to solve for x and y, but we can determine some combinations that solve the problem.
Solving for x:
x=10-4y
Since both x and y are integers and cannot be negative:
10-4y≥0
Swapping sides:
4y≤10
Dividing by 4:
y≤2.5
Thus, y can only have the values {0,1,2}
For y=0
x=10-4*0=10
x=10
For y=1
x=10-4*1=6
x=6
For y=2
x=10-4*2=2
x=2
Thus, the possible combinations are:
0 $20 bills and 10 $5 bills
1 $20 bills and 6 $5 bills
2 $20 bills and 2 $5 bills
You can see how the difference between two consecutive terms is constantly increasing:
So, for the next terms we'll have to add +9, +11, +13 and so on.
Also, note that 
is obtained by adding the 2nd odd number to 
, 
is obtained by adding the 3rd odd number to , and so on.
So, the recursive formula is
For the explicit formula, recall that the sum of the first n odd numbers is n squared. Taking into account the fact that we're not starting from 1, we have
4b - 6b + 19
Answer : -2b + 19
