19/01/04 13:57:39.89 4y9oavEG.net
>>98
nが2つずれた...orz
{1/(1-x-2xx) - 1}/x = (1+2x)/{(1-2x)(1+x)} = (1/3){4/(1-2x) - 1/(1+x)} = (1/3)Σ[n=1,∞] {2^(n+2) - (-1)^n} x^n,
答 {2^(n+2) - (-1)^(n+2)}/3.
19/01/04 13:57:39.89 4y9oavEG.net
>>98
nが2つずれた...orz
{1/(1-x-2xx) - 1}/x = (1+2x)/{(1-2x)(1+x)} = (1/3){4/(1-2x) - 1/(1+x)} = (1/3)Σ[n=1,∞] {2^(n+2) - (-1)^n} x^n,
答 {2^(n+2) - (-1)^(n+2)}/3.