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AP EAMCET202422 May 2024Evening ShiftMathematicsBinomial TheoremActual

If the coefficients of (2 r+6)^ th and (r-1)^ th terms in the expansion of (1+x)²¹ are equal, then the value of r=

Options

  1. A7
  2. B5
  3. C6
  4. D8

Correct answer

C. 6

Step-by-step solution

General term of (1+x)²¹ is T _ r +1 = ²¹ C _ r x^ r Coefficient of (2 r+6)^ th term = Coeff. of (r-1)^ th term 2 r+5=21-(r-2) r =6

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