Wednesday, April 3, 2013

log x + log 2x = 3 log 2 find x values

We'll start by imposing constraints of existence of
logarithms:


x>0


2x>0


The
interval of admissible values of x is (0 , +infinite).


Now,
we'll solve the equation. We'll start by applying the power property of
logarithms:


3 log 2 = log 2^3 = log
8


Now, we'll subtract log 2x both
sides:


log x = log 8 - log
2x


We'll apply the quotient rule of
logarithms:


log a - log b = log
a/b


log x = log 8/2x


log x =
log 4/x


Since the bases are matching, we'll apply the one
to one property:


x = 4/x


x^2 =
4


x1 = +sqrt4


x1 =
+2


x2 = -2


We'll reject the
second solution because it doesn't belong to the interval of admissible
values.


The only solution of the equation is
x = 2.

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