If (a_n=2n^2+3n-4), what is the value of (a_8-a_5)?
Answer and explanation
Correct answer: 87
Given \(a_n=2n^2+3n-4\), \(a_8=2(8)^2+3(8)-4=128+24-4=148\) and \(a_5=2(5)^2+3(5)-4=50+15-4=61\). Therefore, \(a_8-a_5=148-61=87\). Option 84 may seem close, but it does not result from evaluating both terms correctly. Exam tip: calculate each required term separately before finding their difference.
Frequently asked questions
What is the correct answer to this question?
87
Why is this the correct answer?
Given \(a_n=2n^2+3n-4\), \(a_8=2(8)^2+3(8)-4=128+24-4=148\) and \(a_5=2(5)^2+3(5)-4=50+15-4=61\). Therefore, \(a_8-a_5=148-61=87\). Option 84 may seem close, but it does not result from evaluating both terms correctly. Exam tip: calculate each required term separately before finding 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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