Describe how
human ecological
footprint can be
used to assess our
sustainability

answer; /// i believe the correct answer is : /// experience less symptom relief; ///

it would take 95 years for that supernova to be visible on earth, so the year would be about 2113. i hope i did my calculation right.

to answer your question:

f(x)= a^x.  if x=0, f(x)=1  if x=1, f(x)=a  if x=1, f(x)=a^a