Question 365859
b) Answer is a/b, by L'Hopital's rule.
c) Limit does not exist: left and right hand limits are not the same.  Right hand limit is 1, while the left hand limit is -1.
d) {{{ (1-2/x)/(1-4/x^2) = 1/(1+2/x) }}}.  Therefore the limit is  {{{ 1/(1+2/2) = 1/(1+1) = 1/2 }}}