A) 2
B) 4
C) 6
D) - 9
Correct Answer: C
Solution :
Either \[r+3=2r-6\] or \[r+3+2r-6=15,\,\,(\because {{\,}^{n}}{{C}_{r}}={{\,}^{n}}{{C}_{n-r}})\] Þ \[r=9\] or\[r=6\].You need to login to perform this action.
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