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If ""^(n)C(r -1) = 36, ""^(n)C(r) = 84 "...

If `""^(n)C_(r -1) = 36, ""^(n)C_(r) = 84 " and " ""^(n)C_(r +1) = 126`, then find the value of `""^(r)C_(2)`.

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The correct Answer is:
n=9 and r=3
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