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In(5x-1)=in(3x+2) extraneous solution

1 Answer

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\ln(5x-1)=\ln(3x+2)

First note that the left side exists only for
5x-1>0, or
x>\frac15, and the right side exists only for
3x+2>0, or
x>-\frac23. Then any solution to this equation is extraneous if we find
x\le\frac15.

Write both sides as powers of
e to eliminate the logarithms:


e^(\ln(5x-1))=e^(\ln(3x+2))\implies5x-1=3x+2

Simplify and solve:


2x=3\implies x=\frac32

No extraneous solutions here because the one found is larger than 1/5.

answered
User J Griffiths
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