Which general term is correct for the sequence (5,8,13,20,\ldots)?
Answer and explanation
Correct answer: \(a_n=n^2+4\)
The correct general term is \(a_n=n^2+4\). Substituting \(n=1,2,3,4\) gives \(5,8,13,20\), respectively. The closest option, \(a_n=n^2+3\), gives \(4\) as the first term when \(n=1\), so it is incorrect. Exam tip: test a proposed general term by substituting the first two or three values of \(n\).
Frequently asked questions
What is the correct answer to this question?
\(a_n=n^2+4\)
Why is this the correct answer?
The correct general term is \(a_n=n^2+4\). Substituting \(n=1,2,3,4\) gives \(5,8,13,20\), respectively. The closest option, \(a_n=n^2+3\), gives \(4\) as the first term when \(n=1\), so it is incorrect. Exam tip: test a proposed general term by substituting the first two or three values of \(n\).
Which subject and chapter does this question cover?
This is a Class 9 Mathematics question. Chapter: Sequences and Progressions. Topic: Explicit or general rule.
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