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| 1. |
n-4C4=15 |
| Answer» (n-4)!/4!(n-4-4)! = 15(n-4)!/4!(n-8)! = 15(n-4)!/24(n-8)! = 15(n-4)!/(n-8)(n-7)(n-6)(n-5)(n-4)! = 15×24(n-8)(n-7)(n-6)(n-5) = 360[n = 10] answer. | |