9. 记 S(x) = ∑ x^n/(n+2)， x = 0 时 S(0) = 0。x ≠ 0 时，记 T(x) = S(x)x^2 = ∑ x^(n+2)/(n+2)T'(x) = ∑ x^(n+1) = x/(1-x) = -1 + 1/(1-x), (-1T(x) = ∫<0, x> [-t+1/(1-t)]dt + T(0) = - x - ln(1-x),S(x) = -1/x - ln(1-x)/x^2, (-1
