Imran and Aubrey were asked to find an explicit formula for the sequence 14,5,−4,−13,…, where the first term should be g(1).Imran said the formula is g(n)=14−9(n−1).Aubrey said the formula is g(n)=14−9n.Which one of them is right?Choose 1 answer:(A) Only Imran(B) Only Aubrey(C) Both Imran and Aubrey(D) Neither Imran nor Aubrey
Q. Imran and Aubrey were asked to find an explicit formula for the sequence 14,5,−4,−13,…, where the first term should be g(1).Imran said the formula is g(n)=14−9(n−1).Aubrey said the formula is g(n)=14−9n.Which one of them is right?Choose 1 answer:(A) Only Imran(B) Only Aubrey(C) Both Imran and Aubrey(D) Neither Imran nor Aubrey
Identify type of sequence: Identify the type of sequence. The sequence 14,5,−4,−13,ext... has a constant difference between terms, which makes it an arithmetic sequence.
Determine common difference: Determine the common difference d of the sequence. The difference between the first term 14 and the second term 5 is 5−14=−9. This is the common difference.
Use arithmetic sequence formula: Use the arithmetic sequence formula to find the nth term: g(n)=g(1)+(n−1)d. Here, g(1) is the first term, which is 14, and d is the common difference, which we found to be −9.
Substitute values into formula: Substitute the known values into the formula to get Imran's proposed formula: g(n)=14+(n−1)(−9). Simplify the formula to get g(n)=14−9(n−1).
Check Imran's formula: Check Imran's formula by plugging in n=2 to see if it gives the second term of the sequence: g(2)=14−9(2−1)=14−9=5. This matches the second term of the sequence, so Imran's formula seems correct so far.
Check Aubrey's formula: Now, check Aubrey's formula by plugging in n=1 to see if it gives the first term of the sequence: g(1)=14−9(1)=14−9=5. This does not match the first term of the sequence, which should be 14. Therefore, Aubrey's formula is incorrect.
Correct answer: Since Imran's formula gives the correct terms for the sequence and Aubrey's does not, the correct answer is that only Imran is right.
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