Question

如何将函数f(z)= 1/[(z-1)(z-2)]在0

Answer 1

f(z)= 1/[(z-1)(z-2)]

=1/(z-2) - 1/(z-1)

=(-1/2)*1/(1-z/2) + 1/(1-z)

=-1/2 Σ(z/2)^n + Σz^n

求和号都是从n=0到+∞