If (a_n=6n-8), what is (a_{3n-2})?
Answer and explanation
Correct answer: \(18n-20\)
Given \(a_n=6n-8\), substitute the entire index \(3n-2\) for \(n\): \(a_{3n-2}=6(3n-2)-8=18n-12-8=18n-20\). Hence, \(18n-20\) is correct. The option \(18n-12\) results from forgetting to subtract the final 8. Exam tip: always enclose a compound index in brackets before simplifying.
Frequently asked questions
What is the correct answer to this question?
\(18n-20\)
Why is this the correct answer?
Given \(a_n=6n-8\), substitute the entire index \(3n-2\) for \(n\): \(a_{3n-2}=6(3n-2)-8=18n-12-8=18n-20\). Hence, \(18n-20\) is correct. The option \(18n-12\) results from forgetting to subtract the final 8. Exam tip: always enclose a compound index in brackets before simplifying.
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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