If (a_n=2n^3-n), what is the value of (a_4-a_2)?
Answer and explanation
Correct answer: 110
Given \(a_n=2n^3-n\), \(a_4=2(4)^3-4=128-4=124\) and \(a_2=2(2)^3-2=16-2=14\). Therefore, \(a_4-a_2=124-14=110\). A nearby choice such as 108 can result from an error in evaluating the cube or subtracting. Exam tip: find each required term separately before taking their difference.
Frequently asked questions
What is the correct answer to this question?
110
Why is this the correct answer?
Given \(a_n=2n^3-n\), \(a_4=2(4)^3-4=128-4=124\) and \(a_2=2(2)^3-2=16-2=14\). Therefore, \(a_4-a_2=124-14=110\). A nearby choice such as 108 can result from an error in evaluating the cube or subtracting. Exam tip: find each required term separately before taking their difference.
Which subject and chapter does this question cover?
This is a Class 9 Mathematics question. Chapter: Sequences and Progressions. Topic: nth term.
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