利用极限
lim x->无穷 (1-x)^(1/x)=1/e
lim(x→∞)(1-kx)∧(1/x)
=lim(x→∞)[(1-kx)∧(1/(kx))]^k
=[lim(x→∞)(1-kx)∧(1/(kx))]^k
=[e^(-1)]^k
=e^(-k)