If (a_n=3n^2-2n+5), what are the first three terms?
Answer and explanation
Correct answer: (6, 13, 26)
Given \(a_n=3n^2-2n+5\), substitute \(n=1\), \(2\), and \(3\): \(a_1=3(1)^2-2(1)+5=6\), \(a_2=3(2)^2-2(2)+5=13\), and \(a_3=3(3)^2-2(3)+5=26\). Thus, the first three terms are \((6, 13, 26)\). Option D has 14 as the second term, but correct substitution gives 13. Exam tip: substitute each value of \(n\) separately, applying the square and multiplication first.
Frequently asked questions
What is the correct answer to this question?
(6, 13, 26)
Why is this the correct answer?
Given \(a_n=3n^2-2n+5\), substitute \(n=1\), \(2\), and \(3\): \(a_1=3(1)^2-2(1)+5=6\), \(a_2=3(2)^2-2(2)+5=13\), and \(a_3=3(3)^2-2(3)+5=26\). Thus, the first three terms are \((6, 13, 26)\). Option D has 14 as the second term, but correct substitution gives 13. Exam tip: substitute each value of \(n\) separately, applying the square and multiplication first.
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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