So I need to solve log(x+9)=2, the answer is 81 but I have no idea how to get to that. Help please?

Question

hafeda · Answer

u sure the answer is 81 or 91. cuz i am getting 91

dustin_whitelock · Answer

ANS should be 91.

gracie007 · Answer

it's 91, i had a typo

hafeda · Answer

so do u know how to solve it, or do i post a solution

gracie007 · Answer

i have no idea how to solve it.

hafeda · Answer

log(x+9) = 2 
the base of the log is 10, because a log with no base indicated it is always 10. 
Method 1 :  
you can bring the base of the log which is 10 to the other side of the equation which will look like as follow:
x+9 = 10^2 (log is gone ) 
x+9 = 100 ( Subtract 9 from both side ) 
x= 100 - 9 
x= 91. 

Method 2: 
You can rise both side of the equation by 10, which will look as follow: 

10^log(x+9) = 10^2 ( Now we can use the inverse of log aka antilog which is 10^log n )
x+9 = 100 (by this logic the log and 10 will cancel each other out)
x= 100- 9
x=91

IF u have any question please ask, or need more explanation :D