Thursday, April 3, 2014

Please solve for x. ln(x+2) - ln(3x + 1) = 4

First, let's impose the constraints of existence of
logarithms:


x+2>0


x>-2


and


3x+1>0


3x>-1


x>-1/3


The
common interval of values that satisfies both constraints is (-1/3 ,
+inf.).


Now, we can solve the equation by subtracting both
sides the value ln(x+2).


We'll
get:


- ln (3x + 1) = 4 -
ln(x+2)


We'll multiply both sides by
-1:


ln (3x + 1) = -4 +
ln(x+2)


We'll write -4
as:


-4*1 = -4*ln e = ln
(e^-4)


We'll re-write the
equation:


ln (3x + 1) = ln (e^-4) +
ln(x+2)


We'll apply the product property to the right side
of the eq.:


ln (3x + 1) = ln
[(e^-4)*(x+2)]


Because the bases of the logarithms are
matching, we'll apply one to one property:


3x+ 1  = x/e^4 +
2/e^4


We'll subtract both sides
x/e^4:


3x - x/e^4 + 1 =
2/e^4


We'll re-write the
eq.:


3x*e^4 - x = 2 -
e^4


We'll factorize to the left
side:


x*(3e^4 - 1) =
2-e^4


We'll divide by (3e^4 -
1):


x = (2-e^4)/ (3e^4 -
1)>-1/3


So, the solution is
admissible!

No comments:

Post a Comment

Comment on the setting and character of "The Fall of the House of Usher."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...