Mrs. Reid is going on a trip. She has 9 books that she hasn't read yet, but she wants to bring only 3 on the trip. In how many w
2 answers:
Answer:
Option B is right.
Step-by-step explanation:
Given that there are totally 9 books unread by Mrs. Reid. OUt of these she wants to take only 3 books on the trip.
For books order does not count.
Hence combinations would be appropriate to calculate.
3 books out of 9 can be selected in
9C 3 ways
No of ways of selecting 3 books for the trip out of 9 =
There are just 84 ways of choosing 3 books to bring on the trip out of 9 unread books.
Option B is right.
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The value of d is -2
Step-by-step explanation:
The nth term of the arithmetic sequence is , where
is the first term
- d is the common difference between each 2 consecutive terms
The nth term of the geometric sequence is , where
- r is the common ratio between each two consecutive terms
∵ of an arithmetic sequence is 1
∵ The common difference is d, where d ≠ 0
∵ ,
,
are the first 3 terms of a geometric sequence
∵ = 1 + (2 - 1)d
∴ = 1 + d
∵ = 1 + (3 - 1)d
∴ = 1 + 2d
∵ = 1 + (6 - 1)d
∴ = 1 + 5d
∴ The first 3 terms of the geometric sequence are (1 + d) , (1 + 2d) ,
(1 + 5d)
∵ The common ratio in the geometric sequence is
∴
- Use cross multiplication with the equal fractions
∵
∴ (1 + 2d)(1 + 2d) = (1 + d)(1 + 5d)
∴ 1 + 2d + 2d + 4d² = 1 + 5d + d + 5d²
- Add like terms in each side
∴ 1 + 4d + 4d² = 1 + 6d + 5d²
- Subtract 1 from both sides
∴ 4d + 4d² = 6d + 5d²
- Subtract 4d from both sides
∴ 4d² = 2d + 5d²
- Subtract 4d² from each side
∴ 0 = 2d + d²
- Take d as a common factor
∴ 0 = d(2 + d)
- Equate each factor by 0
∴ d = 0 but we will reject it because d ≠ 0
∴ 2 + d = 0
- Subtract 2 from both sides
∴ d = -2
The value of d is -2
Learn more:
You can learn more about the sequence in brainly.com/question/1522572
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