Saturday, February 28, 2015

Solve for x log2 x + log4 x + log8 x =11/6

First, we'll impose the constraints of existence of
logarithms:


x>0


Now,
we'll change the bases of logarithms to base 2:


log2 x =
log4 x*log2 4


log4 x = log2 x/log2
(2^2)


log4 x = log2 x/2log2
2


But log2 2 = 1


log4 x = log2
x/2


log2 x = log8 x*log2
8


log8 x = log2 x/3log2 2


log8
x = log2 x/3


We'll re-write the
equation


log2 x + (log2 x)/2 + (log2 x)/3 =
11/6


We'll multiply by 6 both
sides:


6 log2 x + 3 log2 x + 2 log2 x  =
11


We'll add like
terms:


11 log2 x = 11


We'll
divide by 11:


log2 x = 1


x =
2^1


x = 2


Since 2 belongs to
the interval of admissible values, we'll validate it as solution of the
equation:


x =
2

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