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KCET2007MathematicsSequences and Series

1 2 5 + 1 5 8 + 1 8 11 + 1 (3 n-1)(3 n+2) is equal to

Options

  1. An 6 n-4
  2. Bn 6 n+3
  3. Cn 6 n+4
  4. Dn+1 6 n+4

Correct answer

C. n 6 n+4

Step-by-step solution

Given, 1 2 5 + 1 5 8 + 1 8 11 + array r 5 8 8 11 = 1 3 [ ( 1 2 - 1 5 )+ 1 (3 n-1)(3 n+2) . + + ( 1 5 - 1 8 )+ ( 1 8 - 1 11 ) . .+ - 1 3 n+2 ) ] array aligned &= 1 3 [ 1 2 - 1 3 n+2 ] &= 3 n+2-2 6(3 n+2) = n 6 n+4 aligned

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