Tuesday, April 23, 2013

What is x if log(x+1) (x^2-3x+2)=log(x+1) (x^2-2x), if x+1 is the base of logarithm?

We'll impose the constraints of existence of
logarithms.


The base has to be positive and it is different
from
1.


x+1>0


x>-1


x
different from 0.


Now, the arguments have to be
positive:


x^2-3x+2>0


The
expression is positive if x is in the ranges
(-inf.,1)U(2,+inf.)


x^2-2x>0


The
expression is positive if x is in the ranges
(-inf.,0)U(2,+inf.)


The common intervals of admissible
values for x are:


(-1 ; 0)U(2 ;
+infinite)


Now, we'll solve the
equation.


Since the logarithms have matching bases, we'll
apply one to one property:


x^2-3x+2 =
x^2-2x


We'll eliminate x^2 both
sides:


-3x + 2 + 2x = 0


-x + 2
= 0


-x = -2


x =
2


Since 2 doesn't belong to the intervals of admissible
values, we'll reject it.


The equation has no
solutions.

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