Thursday, August 7, 2014

Evaluate the limit of the function (x^2-3x+2)/(x^2-4) using L'Hospital rule.

You did not mentioned the accumulation point. Though,
L'Hospital rule is used only in case of indetermination, so the accumulation point can
only be a common solution of denominator and numerator of the
fraction.


We'll calculate the roots of the
equations:


x^2-3x+2 = 0


x1 =
[3 + sqrt(9 - 8)]/2


x1 =
(3+1)/2


x1 = 2


x2 =
1


We'll calculate the roots of
denominator:


x^2 - 4 = 0


Since
it is a difference of squares, we'll re-write it as a
product:


(x-2)(x+2) = 0


x - 2
= 0


x = 2


x + 2 =
0


x = -2


We notice that the
common root for both is x = 2.


We'll conclude that the
accumulation point is x = 2, so x->2


We'll evaluate
the limit:


lim (x^2-3x+2)/(x^2-4) = (4 - 6 + 2)/(4 - 4) =
0/0


We'll apply L'Hospital
rule:


lim (x^2-3x+2)/(x^2-4) = lim
(x^2-3x+2)'/(x^2-4)'


lim (x^2-3x+2)'/(x^2-4)' = lim (2x -
3)/2x


We'll substitute x by
2:


lim (2x - 3)/2x = (4 -
3)/4


lim (2x - 3)/2x =
1/4


The limit of the function is: lim
(x^2-3x+2)/(x^2-4) = 1/4.

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