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AP EAMCET20225 Jul 2022Evening ShiftMathematicsBinomial TheoremActual

If ^9 C₃+ ^9 C₅= ¹⁰ C_r for some r N , then r=

Options

  1. A3
  2. B4
  3. C5
  4. D7

Correct answer

B. 4

Step-by-step solution

^n C _r= ^n C _ n-r aligned & ^9 C ₅= ^9 C ₄ & ^9 C ₃+ ^9 C ₅= ^9 C ₃+ ^9 C ₄ & = ¹⁰ C ₄ ( ^ n C _ r + ^ n C _ r -1 = ^ n +1 C _ r ) aligned r=4

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