WHAT IS L ALSO TELL ME CHOICE PLZ Consider the series where In this problem you
ID: 2840966 • Letter: W
Question
WHAT IS L
ALSO TELL ME CHOICE PLZ
Explanation / Answer
a_(n) = (-1)^(n) * (n!)^2 * 3^(n) /(2n+1)!
replace n with n+1 to get a_(n+1).
a_(n+1) = (-1)^(n+1) * ((n+1)!)^2 * 3^(n+1) /(2n+3)!
now
divide them:
a_(n+1)/a_n = [(-1)^(n+1) * ((n+1)!)^2 * 3^(n+1) /(2n+3)!] / [(-1)^(n) * (n!)^2 * 3^(n) /(2n+1)!]
= -3(n+1)^2 / [(2n+2)(2n+2)]
L = lim n-->infy 3(n+1)^2 / [(2n+2)(2n+2)]
= lim 1/n-->0 3(1+1/n)^2 / [(2+2/n)(2+2/n)]
= 3(1+0)^2 / [(2+0)(2+0)]
= 3 /4
option A)
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