Thursday, May 29, 2014

Verify if the logarithmic equation has real solutions ? ln(x^2-1)-ln(x-1)=ln(4)

We'll start by imposing constraints for the existence of
the logarithmic functions:


x^2 - 1 >
0


x - 1 > 0


x >
1


The common interval of values of x that make the
logarithmic functions to exist is (1 , +infinite).


We'll
solve the equation applying the quotient property to the left
side:


ln (x^2 - 1)/(x-1) = ln
4


We'll re-write the difference of 2 squares from
numerator:


x^2 - 1 =
(x-1)(x+1)


ln (x-1)(x+1)/(x-1) = ln
4


We'll simplify and we'll
get:


ln (x + 1) = ln 4


Since
the bases are matching, we'll apply one to one rule:


x + 1
= 4


x = 4 - 1


x =
3


Since the value of x belongs to the range
of admissible values, we'll accept x = 3 as a solution of the
equation.

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