2. 5th term of an arithmetic sequence is 28 and its 9th term is 40. (answer with full steps)
a) Find the common difference.
b) Find its 13th term and first term.
c) Is 100 a difference of any two terms of this sequence? Why?
d) Find the algebraic form of this sequence.
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Verified answer
Answer:
Step-by-step explanation:
Let's solve the given arithmetic sequence problem step by step:
a) To find the common difference (d), we can use the formula for the nth term of an arithmetic sequence:
An = A1 + (n - 1)d
where An is the nth term, A1 is the first term, and d is the common difference.
Given that the 5th term (A5) is 28 and the 9th term (A9) is 40, we can write the following equations:
A5 = A1 + 4d ...(1)
A9 = A1 + 8d ...(2)
Substituting the given values:
28 = A1 + 4d ...(1)
40 = A1 + 8d ...(2)
To eliminate A1, subtract equation (1) from equation (2):
40 - 28 = A1 + 8d - (A1 + 4d)
12 = 4d
d = 3
Therefore, the common difference (d) of the arithmetic sequence is 3.
b) To find the 13th term (A13), we use the formula:
A13 = A1 + (13 - 1)d
A13 = A1 + 12d
A13 = A1 + 12(3)
A13 = A1 + 36
To find the first term (A1), we can substitute the common difference (d) into equation (1):
28 = A1 + 4(3)
28 = A1 + 12
A1 = 16
Therefore, the 13th term (A13) is A1 + 36 = 16 + 36 = 52, and the first term (A1) is 16.
c) To determine if 100 is a difference of any two terms in this sequence, we can check if there exists an integer n such that:
An - Am = 100
Substituting the values into the formula:
(A1 + (n - 1)d) - (A1 + (m - 1)d) = 100
Simplifying:
(n - m)d = 100
Since d = 3 (the common difference), we have:
3(n - m) = 100
However, there is no integer value for n and m that satisfies this equation. Therefore, 100 is not the difference of any two terms in this sequence.
d) The algebraic form of this arithmetic sequence can be written as:
An = A1 + (n - 1)d
Substituting the values we found earlier:
An = 16 + (n - 1)3
Therefore, the algebraic form of this sequence is An = 16 + 3n - 3.
Note: In the final equation, the term (3n - 3) can be further simplified or rearranged if desired.
Answer:
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Step-by-step explanation:
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