Which explicit rule is correct for the sequence (5,10,21,44,\ldots)?
Answer and explanation
Correct answer: \(a_n=3\cdot2^n-n\)
Substituting \(n=1,2,3,4\) into \(a_n=3\cdot2^n-n\) gives \(5,10,21,44\), respectively. Hence, option A is correct. Option C gives 3 when \(n=1\), so it does not even produce the first term. Exam tip: verify an explicit rule by checking at least the first three terms.
Frequently asked questions
What is the correct answer to this question?
\(a_n=3\cdot2^n-n\)
Why is this the correct answer?
Substituting \(n=1,2,3,4\) into \(a_n=3\cdot2^n-n\) gives \(5,10,21,44\), respectively. Hence, option A is correct. Option C gives 3 when \(n=1\), so it does not even produce the first term. Exam tip: verify an explicit rule by checking at least the first three terms.
Which subject and chapter does this question cover?
This is a Class 9 Mathematics question. Chapter: Sequences and Progressions. Topic: Explicit or general rule.
Student feedback
Was this question useful?
👍 0 Helpful 👎 0 Not helpful
Yes 0% No 0%
0 responsesStudent Reviews
No published reviews yet.
