solve:

log21 (x-84) = 3- log21 (x)

Question

solve:

log21 (x-84) = 3- log21 (x)

ganeshie8 · Answer

collect all logs on one side

ganeshie8 · Answer

and change the equation to exponent form

ganeshie8 · Answer

start by adding log21 (x) both sides

anonymous · Answer

x-84 = 9261 - (x)  ??

ganeshie8 · Answer

Very good try, but no !

ganeshie8 · Answer

you're very close  :) could u show how u got that ha ?

anonymous · Answer

YEAH... but i think i got something better...

u said to move all logs to one said.. so i got:

log21 (x^2-84x) = 3

anonymous · Answer

because I know that what I did its wrong.. cause I get stuck there with a wrong answer..

ganeshie8 · Answer

looks better :)

anonymous · Answer

then I will eliminate the log21 and get a quadratic eq right? 

x^2-84x-9261 = 0 and just solve for it i guess

ganeshie8 · Answer

Excellent !
and you know very well how to solve a quadratic

anonymous · Answer

yah :) ... let me do it quick

ganeshie8 · Answer

okay, whenever u solve log/radical equations u may get `extraneous solutions`
so you may need to choose the right one...

anonymous · Answer

yeha... solving it i got 148.8 , but my answer on the book says 147 ?.?

ganeshie8 · Answer

for example :  log cannot suck in negative numbers, so u need to make sure that u dont input negative numbers into log

ganeshie8 · Answer

anonymous · Answer

that site is niceeee... yeah i got that... perfect.. jsut misscalculated.. :D thxs once again :)

ganeshie8 · Answer

np.. u wlc :)