If (a_n=3n^2-2), what is (a_4+a_5)?
Answer and explanation
Correct answer: 119
Given \(a_n=3n^2-2\), \(a_4=3(4)^2-2=46\) and \(a_5=3(5)^2-2=73\). Therefore, \(a_4+a_5=46+73=119\), so option C is correct. A value such as 115 can result from an error while squaring or multiplying for \(a_5\). Exam tip: substitute the value of \(n\), evaluate the square first, and then perform the remaining operations.
Frequently asked questions
What is the correct answer to this question?
119
Why is this the correct answer?
Given \(a_n=3n^2-2\), \(a_4=3(4)^2-2=46\) and \(a_5=3(5)^2-2=73\). Therefore, \(a_4+a_5=46+73=119\), so option C is correct. A value such as 115 can result from an error while squaring or multiplying for \(a_5\). Exam tip: substitute the value of \(n\), evaluate the square first, and then perform the remaining operations.
Which subject and chapter does this question cover?
This is a Class 9 Mathematics question. Chapter: Sequences and Progressions. Topic: Explicit or general rule.
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