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If (a_n=3n^2+4n), what is the value of (a_7-a_4)?
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Answer and explanation
Correct answer: 111
Given \(a_n=3n^2+4n\), \(a_7=3(7)^2+4(7)=147+28=175\) and \(a_4=3(4)^2+4(4)=48+16=64\). Therefore, \(a_7-a_4=175-64=111\). An answer such as 108 can result from an error while evaluating \(7^2\) or \(4^2\). Exam tip: calculate the two terms separately before subtracting.
Frequently asked questions
What is the correct answer to this question?
111
Why is this the correct answer?
Given \(a_n=3n^2+4n\), \(a_7=3(7)^2+4(7)=147+28=175\) and \(a_4=3(4)^2+4(4)=48+16=64\). Therefore, \(a_7-a_4=175-64=111\). An answer such as 108 can result from an error while evaluating \(7^2\) or \(4^2\). Exam tip: calculate the two terms separately before subtracting.
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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