Help! A logarithm that won't be solved

G

Guest

Guest
The problem is -

log(3x+3) - 2log(x+1)=2log3

The answer is 2/3 and 1 but I keep getting 1 and 4.

Please help me!
 
You can check your answers to any "solving" problem by plugging them back into the original problem. In your case:

. . . . .x = 1:

. . . . .log(3 + 3) - 2log(4) ?=? 2log(3)
. . . . .log(6) - log(16) ?=? log(9)
. . . . .log(6/16) ?=? log(9)
. . . . .log(3/8) ?=? log(9)

Since 3/8 does not equal 9, your solution is unlikely to be correct. On the other hand:

. . . . .x = 2/3:

. . . . .log(2 + 3) - 2log(2/3 + 1) ?=? 2log(3)
. . . . .log(5) - 2log(5/3) ?=? log(9)
. . . . .log(5) - log(25/9) ?=? log(9)
. . . . .log((5/1)/(25/9)) ?=? log(9)
. . . . .log(9) ?=? log(9)

So the book's solution is correct.

Without seeing your work, it is difficult to suggest where you may have made an error.

Eliz.

Edit: Please post any follow-ups to your other posting of this exercise.
 
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