Thursday, October 28, 2010

5 log x - log x^3 = log ( 1-2x) find x

We'll impose constraints of existence of
logarithms:


x>0


1-2x>0


-2x>-1


2x<1


x<1/2


The
interval of admissible values of x is (0 , 1/2).


5 log x -
log x^3 = log ( 1-2x) 


We'll use power property of
logarithms for the first term:


5 log x = log
x^5


log x^5- log x^3 = log (
1-2x) 


We'll add log x^3 both
sides:


log x^5 = log ( 1-2x)  + log
x^3


We'll use the product property
of  logarithms:


log a + log b = log
a*b


We'll put a=( 1-2x)  and
b=x^3


log ( 1-2x)  + log x^3 = log
x^3*(1-2x) 


The equation will
become:


log x^5 = log
x^3*(1-2x) 


Since the bases are matching, we'll use one to
one property:


x^5 = 
x^3*(1-2x) 


We'll divide by
x^3:


x^2 = 1 - 2x


We'll
subtract 1-2x:


x^2 + 2x - 1 =
0


x1 = [4-sqrt(4+4)]/2


x1 =
(4-2sqrt2)/2


x1 =
2-sqrt2


x2=2+sqrt2


Since
neither of x values belong to the interval of admissible values for x, the equation has
no solutions.

No comments:

Post a Comment

Comment on the setting and character of &quot;The Fall of the House of Usher.&quot;How does setting act as a character?

Excellent observation, as it identifies how the settings of Poe's stories reflect the characters of their protagonists. Whet...