If (a_n=3^n-2n+1), what is the value of (a_4)?
Answer and explanation
Correct answer: 74
Given \(a_n=3^n-2n+1\), substitute \(n=4\): \(a_4=3^4-2(4)+1=81-8+1=74\). Therefore, 74 is the correct answer. The value 72 would result from omitting the final \(+1\), so it is incorrect. Exam tip: After substituting the term number, evaluate the exponent and multiplication in brackets carefully.
Frequently asked questions
What is the correct answer to this question?
74
Why is this the correct answer?
Given \(a_n=3^n-2n+1\), substitute \(n=4\): \(a_4=3^4-2(4)+1=81-8+1=74\). Therefore, 74 is the correct answer. The value 72 would result from omitting the final \(+1\), so it is incorrect. Exam tip: After substituting the term number, evaluate the exponent and multiplication in brackets carefully.
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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