Wednesday, October 29, 2014

Using l'Hospital theorem evaluate the limit of (x^2+11x-12)/(x-1), for x->1.

We know that l'Hospital theorem could be applied if the
limit gives an indetermination.


We'll verify if the limit
exists, for x = 1.


We'll substitute x by 1 in the
expression of the function.


lim y = lim
(x^2+11x-12)/(x-1)


lim (x^2+11x-12)/(x-1) = 
(1+11-12)/(1-1) = 0/0


We've get an indetermination
case.


We could solve the problem in 2 ways, at
least.


We'll apply L'Hospital
rule:


lim f(x)/g(x) = lim
f'(x)/g'(x)


f(x) = x^2+11x-12 => f'(x) =
2x+11


g(x) = x-1 => g'(x) =
1


lim (x^2+11x-12)/(x-1) = lim
(2x+11)


lim (x^2+11x-12)/(x-1) = 2*1 +
11


lim (x^2+11x-12)/(x-1) =
13

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