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A couple logarithm questions?
When I try to work out log4 (x+3)-log4 x = 3, I get the answer 1/21. See, that's one of the answers on my test but apparently it's wrong. The other options are 3/64, 3/2, and -1/3. Do one of those three sound right? I just don't see it. :/
Also, log3 (x+6)-log3 x=2. The answer I get is 3/4 but apparently that's not right either, even though that's an option.
1 Answer
- I'm with StupidLv 79 years agoFavorite Answer
your answer in both cases is correct
log_4(x + 3) - log_4(x) = 3
log_4((x + 3) / x) = 3
(x + 3) / x = 4³
x + 3 = 64x
3 = 63x
1/21 = x
see
http://www.wolframalpha.com/input/?i=log_4%28x+%2B...
log_3(x + 6) - log_3(x) = 2
similar to above
x = 3/4
see
http://www.wolframalpha.com/input/?i=log_3%28x+%2B...
must be an error on the test site.
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