\(^2log(x) = ^4log(4x) \)
i wonder how do i get the x because i know the answer is 4 but i dont know how to come to this answer?
thanks in advance
Solve for x:
(log(x))/(log(2))=(log(4 x))/(log(4))
Subtract (log(4 x))/(log(4)) from both sides:
(log(x))/(log(2))-(log(4 x))/(log(4))=0
Bring (log(x))/(log(2))-(log(4 x))/(log(4)) together using the common denominator log(2) log(4):
-(log(2) log(4 x)-log(4) log(x))/(log(2) log(4))=0
Divide both sides by -1/(log(2) log(4)):
log(2) log(4 x)-log(4) log(x)=0
log(2) log(4 x)-log(4) log(x)=log(x^(-2 log(2)))+log(4^(log(2)) x^(log(2)))=log(4^(log(2)) x^(-log(2))):
log(4^(log(2)) x^(-log(2)))=0
Cancel logarithms by taking exp of both sides:
4^(log(2)) x^(-log(2))=1
Divide both sides by 4^(log(2)):
x^(-log(2))=4^(-log(2))
Take reciporicals of both sides:
x^(log(2))=4^(log(2))
Raise both sides to the power of 1/(log(2)):
Answer: | x=4
Why are the 2 and the 4 written as strange superscripts ?
Our guest seems to understand but I don't
I think this is meant to be:
\(\log_2x=\log_4{4x}\)
Let:
\(a=\log_2x\\x=2^a\)
So, also:
\(a=\log_4{4x}\\4x=4^a\\x=4^{a-1}\\x=2^{2(a-1)}\)
Hence we must have:
a = 2(a - 1) so that a = 2, which means x = 2a or x = 4
.
Here's another approach....using Alan's interpretation
log2x = log4(4x)
log2x = log44 + log4x
log2x - log4x = log44
log2x - log4x = 1
logx/log2 - logx/log 4 = 1
logx [ log4 - log 2] / [log2 * log 4] = 1
logx = [log2 * log4] / [ log4 - log2]
logx = [log2 * log4] / [log (4/2)]
logx = [log2 * log4] / [log2]
log x = log 4
x = 4