Tuesday, December 3, 2013

Evaluate the limit of the function [(x+5)/(x+2)]^(2x+1) x approaches to + infinite.

The limit will go to the base and to the
superscript.


The limit of the base
is:


lim (x+5)/(x+2) = lim x(1 + 5/x)/x(1 + 2/x) = lim(1 +
5/x)/(1 + 2/x)=1


The limit of superscript
is:


lim (2x+1) = +infinite


We
notice that we've get an indeterminacy: 1^infinite.


We'll
create remarcable limit "e".


We'll add 1 and subtract 1
inside the brackets of the base:


[1 + (x+5)/(x+2) - 1] = [1
+ (x+5-x-2)/(x+2)] = [1+ 3/(x+2)]


The remarcable limit
is:


lim (1 + 1/x)^x = e,
x->infinite


We'll re-write the
limit:


lim { [1+ 3/(x+2)]^(x+2)/3}^3(2x+1)/(x+2) =
lim { [1+ 3/(x+2)]^(x+2)/3}^ lim 3(2x+1)/(x+2)


lim { [1+
3/(x+2)]^(x+2)/3} = e


The limit of
superscript:


lim 3(2x+1)/(x+2) = lim 3x(2+1/x)/x(1+2/x)
=  lim 3(2+1/x)/(1+2/x) = 6/1


The limit of
the function, when x approaches to +infinite, is:  lim [(x+5)/(x+2)]^(2x+1) =
e^6

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