直接的解法
yma16
2018-11-13 19:31:19
( reads)
1) 1/x + 4/x^2 + 9/x^3 + 16/x^4... = S
2) 1 + 4/x + 9/x^2 + 16/x^3 .. = Sx
1)-2)
3) -1 - 3/x - 5/x^2 - 7/x^3 - ... = S(1-x)
4) -x - 3 - 5x - 7/x^2 - ... = Sx(1-x)
3)-4)
5) x + 2 + 2/x + 2/x^2 + 2/x^3 + ... = S(1-x)^2 , 5)可以给出一样的答案.