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Find n, ` ""^(n+5)P_(n+1)=(11)/(2)(n-1)*""^(n+3)P_(n).` |
Answer» We have, `(.^(n+5)P_(n+1))/(.^(n+3)P_(n))=(11(n-1))/(2)` `implies((n+5)(n+3)^(n+3)P_(n-1))/(.^(n+3)P_(n))=(11(n-1))/(2)` [from note (iii)] `((n+5)(n+4))/((n+3-n+1))=(11(n-1))/(2)` [from note (v)] `implies(n+5)(n+4)=22(n-1)` `impliesn^(2)-13n+42=0` `implies(n-6)(n-7)=0` `thereforen=6.7` |
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