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nP5=42(nP3), find n |
Answer» `nC_5*5! =42*nC_3*3!` `(n!)/(5!(n-5)!)*5! =42*(n!)/(3!(n-3)!*3!` `((n-3)!)/((n-5)!)=42` `n^2-7n+12=42` `(n-10)(n+n)=0` `n=10`. |
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