SOLUTION: ln (x-8) - ln (x+7)= ln (x-10) - ln (x+8)

Algebra ->  Logarithm Solvers, Trainers and Word Problems -> SOLUTION: ln (x-8) - ln (x+7)= ln (x-10) - ln (x+8)      Log On


   

Question 686808: ln (x-8) - ln (x+7)= ln (x-10) - ln (x+8)
Answer by josmiceli(19441) About Me  (Show Source):
You can put this solution on YOUR website!
+ln+%28x-8%29+-+ln+%28x%2B7%29=+ln+%28x-10%29+-+ln+%28x%2B8%29+
+ln%28+%28+x-8+%29+%2F+%28+x%2B7+%29+%29+=+ln%28+%28+x-10%29+%2F+%28+x%2B8+%29+%29+
+%28+x-8+%29+%2F+%28+x%2B7+%29+=+%28+x-10%29+%2F+%28+x%2B8+%29+
Multiply both sides by +%28+x%2B7+%29%2A%28+x%2B8+%29+
+%28+x-8+%29%2A%28+x%2B8+%29+=+%28+x+-10+%29%2A%28+x%2B7+%29+
+x%5E2+-+64+=+x%5E2+-+10x+%2B+7x+-+70+
+-64+=+-3x+-+70+
+3x+=+-70+%2B+64+
+3x+=+-6+
+x+=+-2+
----------
I'm doubtful that this is the right solution.
It works for
+%28+x-8+%29+%2F+%28+x%2B7+%29+=+%28+x-10%29+%2F+%28+x%2B8+%29+
+%28+-2-8+%29+%2F+%28+-2%2B7+%29+=+%28+-2-10%29+%2F+%28+-2%2B8+%29+
+-10+%2F+5+=+-12+%2F+6+
+-2+=+-2+
But it doesn't work for
+ln+%28x-8%29+-+ln+%28x%2B7%29=+ln+%28x-10%29+-+ln+%28x%2B8%29+
+ln+%28-2-8%29+-+ln+%28-2%2B7%29=+ln+%28-2-10%29+-+ln+%28-2%2B8%29+
+ln+%28-10%29+-+ln+%285%29=+ln+%28-12%29+-+ln+%286%29+
There is no log to a positive base that
gives me +-10+ or +-12+
---------------------------
I would get a 2nd opinion on this one