If (a_n=4n+1), what is (a_{2m})?
Answer and explanation
Correct answer: \(8m+1\)
Given \(a_n=4n+1\), substitute the complete index \(2m\) for \(n\): \(a_{2m}=4(2m)+1=8m+1\). Hence, option A is correct. \(4m+1\) would be obtained for the index \(m\), not \(2m\). Exam tip: Always substitute a compound index in brackets.
Frequently asked questions
What is the correct answer to this question?
\(8m+1\)
Why is this the correct answer?
Given \(a_n=4n+1\), substitute the complete index \(2m\) for \(n\): \(a_{2m}=4(2m)+1=8m+1\). Hence, option A is correct. \(4m+1\) would be obtained for the index \(m\), not \(2m\). Exam tip: Always substitute a compound index in brackets.
Which subject and chapter does this question cover?
This is a Class 9 Mathematics question. Chapter: Sequences and Progressions. Topic: nth term.
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