0 reads0 ratings0 helpful
If (a_n=4n^2-1), what is the value of (a_5+a_1)?
Advertisement
Answer and explanation
Correct answer: 102
Given \(a_n=4n^2-1\), \(a_5=4(5)^2-1=100-1=99\) and \(a_1=4(1)^2-1=3\). Hence, \(a_5+a_1=99+3=102\). Option 100 is only \(4\times 5^2\); it ignores both the \(-1\) and \(a_1\). Exam tip: Substitute each required value of \(n\) separately before adding the terms.
Frequently asked questions
What is the correct answer to this question?
102
Why is this the correct answer?
Given \(a_n=4n^2-1\), \(a_5=4(5)^2-1=100-1=99\) and \(a_1=4(1)^2-1=3\). Hence, \(a_5+a_1=99+3=102\). Option 100 is only \(4\times 5^2\); it ignores both the \(-1\) and \(a_1\). Exam tip: Substitute each required value of \(n\) separately before adding the 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?
Was this question useful?
👍 0 Helpful 👎 0 Not helpful
Difficulty
Easy0%
Medium0%
Hard0%
Was the explanation clear?
Yes 0% No 0%
0 responsesStudent Reviews
No published reviews yet.
Advertisement