Help with log please urgent!

[lornick]

Hi hopefully someone can help me quickly lol but his is actually doing my head in a little, I need to solve for x.

1. log base 4 (16)=x-3

Answer= 4^x-3=16
x-3 log base 4= 2 log base 4
x= 2 log base 4 - 3 log base 4
x=2 log base 4 / 3 log base 4
x=log base 4 (2/3)
x= -0.6667


I am just trying to make sure I have my head around it correctly. Its strange I can answer most questions with logs that are difficult but when it comes to the simple ones I tend to get a little confused.:lol: I want to apologise for posting up too many questions, I should of read forum rules first I will post others up as this one is answered. Thanks ahead for any help.

 

[lookagain]

Hi hopefully someone can help me quickly lol but his is actually doing my head in a little.


2. log base 3 (10) - log base 3 (x)=log base 3 (5) (just checking with this one that I am correct) \(\displaystyle \ \ \ \) Then you please show your work/solution here first, before someone shows their work for possible confirmation.

If you cant answer 2, 3 and 4 its all good I am just trying to make sure I have my head around it correctly. Its strange I can answer most questions with logs that are difficult but when it comes to the simple ones I tend to get a little confused.:lol:

Please read "Read Before Posting" here: http://www.freemathhelp.com/forum/threads/41536-Read-Before-Posting!!

 

[lornick]

Oops sorry I have edited my question as suggested by the forum rules I apologise for not reading rules first.

 

[stapel]

Hi hopefully someone can help me quickly lol but his is actually doing my head in a little, I need to solve for x.

1. log base 4 (16)=x-3

Answer= 4^x-3=16
x-3 log base 4= 2 log base 4
x= 2 log base 4 - 3 log base 4
x=2 log base 4 / 3 log base 4
x=log base 4 (2/3)
x= -0.6667

If you plug -2/3 in for x in the original equation, do you get a valid equation?

Hint: The log is a power; in this case, it's the power that you'd need to put on 4 to get 16. What power is that? Now set the right-hand side equal to that power (since that IS what the log is), and solve by adding. ;-)

 

[Dale10101]

Note

Hi hopefully someone can help me quickly lol but his is actually doing my head in a little, I need to solve for x.

1. log base 4 (16)=x-3

Answer= 4^x-3=16
x-3 log base 4= 2 log base 4
x= 2 log base 4 - 3 log base 4
x=2 log base 4 / 3 log base 4
x=log base 4 (2/3)
x= -0.6667


I am just trying to make sure I have my head around it correctly. Its strange I can answer most questions with logs that are difficult but when it comes to the simple ones I tend to get a little confused.:lol: I want to apologise for posting up too many questions, I should of read forum rules first I will post others up as this one is answered. Thanks ahead for any help.

16 can be expressed as 4^2, so LOG(16, 4) = 2 => 2 = x-3 i.e then you need to solve for x.