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If (a_n=3^n+2n), what is the value of (a_4)?
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Answer and explanation
Correct answer: 89
Given \(a_n=3^n+2n\), substitute \(n=4\): \(a_4=3^4+2(4)=81+8=89\). Hence, 89 is the correct answer. The value 87 may result from incorrectly taking \(2n\) as 6. Exam tip: Substitute the term number carefully in every part containing \(n\).
Frequently asked questions
What is the correct answer to this question?
89
Why is this the correct answer?
Given \(a_n=3^n+2n\), substitute \(n=4\): \(a_4=3^4+2(4)=81+8=89\). Hence, 89 is the correct answer. The value 87 may result from incorrectly taking \(2n\) as 6. Exam tip: Substitute the term number carefully in every part containing \(n\).
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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