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Class 9MathematicsSequences and Progressionsnth termHardLevel 57
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A sequence has rule (a_n=5n^2+2). Which term is (127)?

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Answer and explanation

Correct answer: 5th

To obtain the value 127, set \(5n^2+2=127\). This gives \(5n^2=125\), so \(n^2=25\) and \(n=5\). Since a term number is a positive integer, the correct answer is the 5th term. The 4th term is \(5\times4^2+2=82\), not 127. Exam tip: equate the given value to \(a_n\) first, then solve for \(n\).

Related tags

SequencesProgressionsNth TermQuadratic SequenceTerm Number

Frequently asked questions

What is the correct answer to this question?

5th

Why is this the correct answer?

To obtain the value 127, set \(5n^2+2=127\). This gives \(5n^2=125\), so \(n^2=25\) and \(n=5\). Since a term number is a positive integer, the correct answer is the 5th term. The 4th term is \(5\times4^2+2=82\), not 127. Exam tip: equate the given value to \(a_n\) first, then solve for \(n\).

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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10 more MCQs
  1. 1In the sequence \((1,4,9,16,\ldots)\), what is the difference between the 15th term and the 14th term?
  2. 2What is the 25th term of the sequence \((-5,-1,3,7,\ldots)\)?
  3. 3If aₙ = n³ − n, what will be the value of a₇ − a₅?
  4. 4What will be the 12th term in the sequence (3, 5, 9, 15, 23, ...)?
  5. 5If a_n = n(n + 2), what will be the value of a_11 − a_8?
  6. 6If a_n = n^2 + 5n - 2, which term is equal to 148?
  7. 7The sequence (3, 8, 15, 24, …) has general term a_n = n² + 2n. Which term is 168?
  8. 8If a_n = n³ + n², what will be the value of a_6 − a_4?
  9. 9If a_n = 4n² − 1, which term is 575?
  10. 10If a_n = n(n + 3), which term is 130?
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