If (a_n=(2n-1)^2), what is the value of (a_5)?
Answer and explanation
Correct answer: 81
Given \(a_n=(2n-1)^2\). Substituting \(n=5\), we get \(a_5=(2\times5-1)^2=(10-1)^2=9^2=81\). Hence, 81 is the correct option. The value 64 would require the expression inside the square to be 8, which it is not. Exam tip: substitute the value of \(n\) first, and then evaluate the exponent.
Frequently asked questions
What is the correct answer to this question?
81
Why is this the correct answer?
Given \(a_n=(2n-1)^2\). Substituting \(n=5\), we get \(a_5=(2\times5-1)^2=(10-1)^2=9^2=81\). Hence, 81 is the correct option. The value 64 would require the expression inside the square to be 8, which it is not. Exam tip: substitute the value of \(n\) first, and then evaluate the exponent.
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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