If (a_n=2n^3+n^2+n), what is the value of (a_3)?
Answer and explanation
Correct answer: 66
Substitute \(n=3\) in the given rule: \(a_3=2(3)^3+(3)^2+3=2\times27+9+3=54+9+3=66\). Therefore, 66 is the correct option. Getting 64 indicates an error in evaluating the cubic term \(2(3)^3\). Exam tip: substitute the value in every term first, then evaluate powers before adding.
Frequently asked questions
What is the correct answer to this question?
66
Why is this the correct answer?
Substitute \(n=3\) in the given rule: \(a_3=2(3)^3+(3)^2+3=2\times27+9+3=54+9+3=66\). Therefore, 66 is the correct option. Getting 64 indicates an error in evaluating the cubic term \(2(3)^3\). Exam tip: substitute the value in every term first, then evaluate powers before adding.
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.
