Sunday, May 26, 2013

log100=2(logx+log5) What is x?

We'll remove the brackets from the right
side:


log100=2(logx+log5)


log100=2logx
+2log5


First, we'll use the power property of logarithms,
for the terms of the expression:


2 log 5 = log
5^2


2log x = log x^2


We'll
re-write the expression:


log100 = log x^2 + log
5^2


Since the bases are matching, we'll use the product
property of logarithms:


log a + log b = log
a*b


We'll put a = x^2 and b =
5^2


log x^2 + log 5^2 = log
x^2*5^2


We'll write the
equation:


log 100 = log
x^2*5^2


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


100 =
x^2*5^2


We'll use symmetric
property:


25x^2 = 100


We'll
divide by 25;


x^2 = 4


x1 =
-2


x2 = 2


Since the solution
of the equtaion must be positive, the first solution x1 = -2, will be
rejected.


The equation will have just a
solution, x = 2.

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