If (a_n=2^n-1), what is the value of (a_4)?
Answer and explanation
Correct answer: 15
Given \(a_n=2^n-1\), substitute \(n=4\): \(a_4=2^4-1=16-1=15\). Therefore, 15 is the correct option. The closest distractor, 16, is only the value of \(2^4\); the subtraction of 1 must still be done. Exam tip: substitute the term number first, then follow the order of operations.
Frequently asked questions
What is the correct answer to this question?
15
Why is this the correct answer?
Given \(a_n=2^n-1\), substitute \(n=4\): \(a_4=2^4-1=16-1=15\). Therefore, 15 is the correct option. The closest distractor, 16, is only the value of \(2^4\); the subtraction of 1 must still be done. Exam tip: substitute the term number first, then follow the order of operations.
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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