求第六题的过程
1个回答
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bn = an.x^n/[n.(2/3)^n]
b(n+1)/bn
=[a(n+1)/an]x . [n/(n+1)]. (3/2)
lim(n->无穷) b(n+1)/bn
=lim(n->无穷) [a(n+1)/an]x . [n/(n+1)]. (3/2)
=(3/2)lim(n->无穷) [a(n+1)/an]x
∑(n:0->无穷) an.x^n 的 收敛半径 = (-3, 3]
=>
∑(n:0->无穷) an.x^n/[n.(2/3)^n]
收敛半径
=(-2, 2]
b(n+1)/bn
=[a(n+1)/an]x . [n/(n+1)]. (3/2)
lim(n->无穷) b(n+1)/bn
=lim(n->无穷) [a(n+1)/an]x . [n/(n+1)]. (3/2)
=(3/2)lim(n->无穷) [a(n+1)/an]x
∑(n:0->无穷) an.x^n 的 收敛半径 = (-3, 3]
=>
∑(n:0->无穷) an.x^n/[n.(2/3)^n]
收敛半径
=(-2, 2]
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