質問: How do you evaluate the limit #(1/(1+r)-1)/r# as r approaches #0#? ==================================================================
回答: #(1/(1+r)-1)/r# #=(1/(1+r)-(1+r)/(1+r))/r# #=((1-(1+r))/(1+r))/r# #=((1-1-r)/(1+r))/r# #=(-r/(1+r))/r# #=-r/(1+r)*1/r# #=-1/(1+r)# Now: #lim_{r->0}-1/(1+r)=-1#