Mathematics
Question:
Find x - logarithmic equation?
Pub
2013-06-12 13:33:13 UTC
Solve log_x(5) - log_5(x) = log_5(1\fifth root of x)
Three answers:
gile
2013-06-13 10:51:40 UTC
I'm assuming that the RHS of the equation reads: logarithm to base 5
of 1 over the fifth root of x, log_5 (1/⁵√x) or log_5 [x^(-1/5)].
log_x (5) - log_5 (x) = log_5 [x^(-1/5)].
Replacing log_x (5) with its equivalent 1/log_5(x)
1/log_5 (x) - log_5 (x) = (-1/5) log_5 (x).
Let log_5(x) = y,
1/y - y = (-1/5)y
1/y = y - (1/5)y
1/y = 4/5y
y² = 5/4
y = ±√(5)/2
Hence
log_5 (x) = ±√(5)/2
x = 5^(±√(5)/2) = √(5)^(±√(5))
x = √(5)^√(5) or x = 1/√(5)^√(5)
Ramin /
2013-06-12 13:52:38 UTC
log_x(5) -1/( log_x(5))=- (1/5) log_x(5)
considering y=log_x(5)
y- 1/y=-y/5
y^2-1=(y^2)/5
4y^2==5
y^2=5/4
y=±(√5)/2
log_5(x)=√5/2
5=x^(√5/2)
x=5^(2/√5)
?
2013-06-12 13:48:31 UTC
log[x] 5 - log[5] x = log[5] √x /5
1/log[5] x - log[5] x = log[5] √x - log[5] 5
1/log[5] x - log[5] x = 1/2 log[5] x - 1
Let log[5] x = a
1/a - a = a/2 - 1
Multiply each term by 2a
2 - 2a^2 = a^2 - 2a
3a^2 - 2a - 2 = 0...not factorisable!
log_5(1\fifth root of x)?? Creating confusion.
Hopefully you get the idea
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