Question:

The general term of a sequence is \( t_n = \frac{n(n+6)}{n+4}, \, n = 1,2,3,\ldots \). If \( t_n = 5 \), then the value of \( n \) is

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Always check domain conditions after solving equations, especially when \( n \) represents term number.
Updated On: Apr 21, 2026
  • \(2 \)
  • \(3 \)
  • \(4 \)
  • \(5 \)
  • \(6 \)
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The Correct Option is C

Solution and Explanation

Concept: Solve the equation \( t_n = 5 \) by simplifying the rational expression.

Step 1:
Set equation.
\[ \frac{n(n+6)}{n+4} = 5 \]

Step 2:
Cross multiply.
\[ n(n+6) = 5(n+4) \]

Step 3:
Simplify.
\[ n^2 + 6n = 5n + 20 \] \[ n^2 + n - 20 = 0 \]

Step 4:
Factorize.
\[ (n+5)(n-4)=0 \]

Step 5:
Find valid solution.
\[ n = -5, 4 \] Since \( n \in \mathbb{N} \), valid solution is: \[ n = 4 \]
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