Question

Are you allowed to do this

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

Please help :)

Answer 1

See:

http://www.jiskha.com/display.cgi?id=1294279972

Answer 2

Some mathteacher published a book some time ago listing all the silly solutions that students had produced.

It actually had it this way

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

(2log(x-1))<b>/log</b> = (log(x+1))<b>/log</b> , then the log/log canceled

2(x-1) = (x+1)
2x - 2 = x+1
x = 3, which by sheer coincidence is the right answer.

Answer 3

My teacher showed us this one:

64/16
= (6)4/1(6) [cancel the 6]
= 4/1
= 4

gets the right answer, but the wrong way.