Answer:
Lower limit of the sum: 0
Upper limit of the sum: 17
Explicit formula: ∑
(3+7i)
Step-by-step explanation:
Noting that each row has 7 more beads than the previous one and that the series also begins with 3, the formula is:
∑
(3+7i)
The lower limit is 0, since 3+ (7 * 0) = 3
When i = 0 you get the value of beads from the first row, when i = 1 you get the value of beads from the second row and so on. Given this, the upper limit is 17.
The answer for your question is q=2
Let x be the value of the third term.
Since it's a geometric sequence, then:
Third term/Second term = Fourth term/Third term
x/20 = 11.25/x
Cross multiplication:
x^2 = 225
x = 15
So since the ratio is constant, then it is
x/20 = 15/20 = 3/4
So the common ratio is 3/4 or 0.75.