SOLUTION: solve log x +log(X-4)= log 5

Algebra ->  Exponential-and-logarithmic-functions -> SOLUTION: solve log x +log(X-4)= log 5      Log On


   

Question 314292: solve log x +log(X-4)= log 5
Answer by Fombitz(32388) About Me  (Show Source):
You can put this solution on YOUR website!
log%28%28x%29%29+%2Blog%28%28x-4%29%29=+log+%28%285%29%29+
log%28%28x%28x-4%29%29%29=log%285%29+
log%28%28x%28x-4%29%2F5%29%29%29=0
x%28x-4%29%2F5=1
x%28x-4%29=5
x%5E2-4x=5
x%5E2-4x-5=0
+%28x%2B1%29%28x-5%29=0

Two solutions:
+x%2B1=0
+x=-1
Not allowed, since log functions require non-negative arguments.
.
.
.
+x-5=0
highlight_green%28x=5%29
.
.
.
Verify the solution.
log%28%285%29%29+%2Blog%28%285-4%29%29=+log+%28%285%29%29+
log%28%285%29%29+%2Blog%28%281%29%29=+log+%28%285%29%29+
log%28%285%29%29+%2B0=+log+%28%285%29%29+
log%28%285%29%29=+log+%28%285%29%29+
True, good solution.