If (a_n=4n^2-1), which is (a_5)?
Answer and explanation
Correct answer: 99
Given \(a_n=4n^2-1\), substitute \(n=5\) to find the fifth term: \(a_5=4(5)^2-1=4\times25-1=99\). Therefore, 99 is correct. The value 101 would result from incorrectly using \(+1\) instead of the final \(-1\). Exam tip: substitute the term number first and evaluate the exponent before other operations.
Frequently asked questions
What is the correct answer to this question?
99
Why is this the correct answer?
Given \(a_n=4n^2-1\), substitute \(n=5\) to find the fifth term: \(a_5=4(5)^2-1=4\times25-1=99\). Therefore, 99 is correct. The value 101 would result from incorrectly using \(+1\) instead of the final \(-1\). Exam tip: substitute the term number first and evaluate the exponent before other operations.
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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