SOLUTION: Solve {{{ log ( 7,(x+8) ) - log ( 7,(x-5) ) = log ( 7,4 ) }}}

Algebra ->  Logarithm Solvers, Trainers and Word Problems -> SOLUTION: Solve {{{ log ( 7,(x+8) ) - log ( 7,(x-5) ) = log ( 7,4 ) }}}      Log On


   

Question 476520: Solve
+log+%28+7%2C%28x%2B8%29+%29+-+log+%28+7%2C%28x-5%29+%29+=+log+%28+7%2C4+%29+
Answer by robertb(5830) About Me  (Show Source):
You can put this solution on YOUR website!
+log+%28+7%2C%28x%2B8%29+%29+-+log+%28+7%2C%28x-5%29+%29+=+log+%28+7%2C4+%29+
==>+log+%28+7%2C%28%28x%2B8%29%2F%28x-5%29%29+%29+=+log+%28+7%2C4+%29+
==>(x+8)/(x-5) = 4, because the logarithmic function is 1-to-1.
==> x + 8 = 4x - 20
==> 28 = 3x
==> x = 28/3.
This value satisfies the original equation, and so is the final answer.