SOLUTION: Solve the equation: 1n x = 1n 2 + 1n (3x - 1) I know the answer is 2/5 from the answers in the back of the book. I need to know how the solution was solved. I really appreci

Algebra ->  Logarithm Solvers, Trainers and Word Problems -> SOLUTION: Solve the equation: 1n x = 1n 2 + 1n (3x - 1) I know the answer is 2/5 from the answers in the back of the book. I need to know how the solution was solved. I really appreci      Log On


   



Question 80458This question is from textbook
: Solve the equation: 1n x = 1n 2 + 1n (3x - 1)
I know the answer is 2/5 from the answers in the back of the book.
I need to know how the solution was solved.
I really appreciate your help.
This question is from textbook

Answer by bucky(2189) About Me  (Show Source):
You can put this solution on YOUR website!
Given:
.
1n x = 1n 2 + 1n %283x+-+1%29
.
Collect the logarithms that contain x on one side of the equation. You can do that by
subtracting ln %283x+-+1%29 from both sides of the equation. When you do that subtraction
you get:
.
ln x - ln %283x+-+1%29 = ln 2
.
Now apply the rule that the difference in two logarithms is the same as the log of their division.
In equation form that rule says:
.
ln a - ln b = ln %28a%2Fb%29
.
With that rule the equation becomes:
.
ln x%2F%283x+-+1%29 = ln 2
.
Look at this carefully ... comparing the left side to the right side. For this to be
true the two logarithms must be equal, and this means that:
.
x%2F%283x+-+1%29+=+2
.
To get rid of the denominator, multiply both sides by the denominator of 3x-1 to
get:
.
%283x-1%29%2A%28x%2F%283x-1%29%29+=+2%2A%283x+-+1%29
.
On the left side the multiplier cancels with the denominator. And multiplying the right
side, gives:
.
cross%283x-1%29%2A%28x%2Fcross%283x-1%29%29+=+6x+-+2
.
and it reduces to:
.
x+=+6x+-+2
.
Solve this as you would any equation. You need to gather all the terms that contain x
on one side of the equation and everything else on the other side. You can do this by
subtracting 6x from both sides to get:
.
+x+-+6x+=+-2
.
combine the terms on the left side and the result is:
.
-5x+=+-2
.
solve for x by dividing both sides by -5 and the outcome is:
.
x+=+-2%2F-5+=+2%2F5
.
and that's how to get the book answer. Hope this helps to familiarize you with logarithms.