AP Calc AB question about tackling MC?

MITer94
Mon, 05 May 2014 22:13:58 +0000

As above, you can only use that rule (L’Hôpital’s) if initially, you obtain 0/0 or infinity/infinity, and if lim_{x -> c} f’(x)/g’(x) exists (see Wikipedia article). It may not work on other cases:

Ex. lim_{x -> 0+} (x^2 + 1)/x. If you plug in x = 0, you obtain 1/0, and blindly taking derivatives of numerator and denominator yields an incorrect answer of 0.