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Provide an Appropriate Response ln2=\ln 2 = \infty - \infty Where Does the Argument Go Wrong

Question 155

Essay

Provide an appropriate response.
-Here is an argument that ln2=\ln 2 = \infty - \infty . Where does the argument go wrong?
ln2=ln1+ln2=ln1ln12\ln 2 = \ln 1 + \ln 2 = \ln 1 - \ln \frac { 1 } { 2 }
=limbln(b1b)ln12= \lim _ { b \rightarrow \infty } \ln \left( \frac { b - 1 } { b } \right) - \ln \frac { 1 } { 2 } =limb[lnx1x]2b= \lim _ { b \rightarrow \infty } \left[ \ln \frac { x - 1 } { x } \right] _ { 2 } ^ { b }
=limb[ln(x1)lnx]2b= \lim _ { b \rightarrow \infty } [ \ln ( x - 1 ) - \ln x ] _ { 2 } ^ { b }
=limb2b(1x11x)dx= \lim _ { b \rightarrow \infty } \int _ { 2 } ^ { b } \left( \frac { 1 } { x - 1 } - \frac { 1 } { x } \right) d x
=2(1x11x)dx= \int _ { 2 } ^ { \infty } \left( \frac { 1 } { x - 1 } - \frac { 1 } { x } \right) d x
Here is an argument that ln2=.\ln 2 = \infty - \infty .
ln2=ln1+ln2=ln1ln12\ln 2 = \ln 1 + \ln 2 = \ln 1 - \ln \frac { 1 } { 2 }
=limbln(b1b)ln12= \lim _ { b \rightarrow \infty } \ln \left( \frac { b - 1 } { b } \right) - \ln \frac { 1 } { 2 }
=limb[lnx1x]2b= \lim _ { b \rightarrow \infty } \left[ \ln \frac { x - 1 } { x } \right] _ { 2 } ^ { b }
=limb[ln(x1)lnx]2b= \lim _ { b \rightarrow \infty } [ \ln ( x - 1 ) - \ln x ] { } _ { 2 } ^ { b }
=limb2b(1x11x)dx= \lim _ { b \rightarrow \infty } \int _ { 2 } ^ { b } \left( \frac { 1 } { x - 1 } - \frac { 1 } { x } \right) d x
=2(1x11x)dx= \int _ { 2 } ^ { \infty } \left( \frac { 1 } { x - 1 } - \frac { 1 } { x } \right) d x
=21x1dx21xdx= \int _ { 2 } ^ { \infty } \frac { 1 } { x - 1 } d x - \int _ { 2 } ^ { \infty } \frac { 1 } { x } d x
=limb[ln(x1)]bblim[lnx]= \lim _ { b \rightarrow \infty } [ \ln ( x - 1 ) ] \frac { b } { b } - \lim [ \ln x ]
== \infty - \infty
=21x1dx21xdx= \int _ { 2 } ^ { \infty } \frac { 1 } { x - 1 } d x - \int _ { 2 } ^ { \infty } \frac { 1 } { x } d x
=limb[ln(x1)]2blimb[lnx]2b= \lim _ { b \rightarrow \infty } [ \ln ( x - 1 ) ] _ { 2 } ^ { b } - \lim _ { b \rightarrow \infty } [ \ln x ] _ { 2 } ^ { b }
== \infty - \infty

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