Monday, February 21, 2011

What are the values of x for log (16) (x^2 + 14x – 2) = log (4) (x – 1)?

log16 ( x^2 + 14x - 2) = log 4
(x-1)


First we will use the logarithm properties to
solve.


We will rewrite log
16


We know that log a b = log c b/ log c
a


==> log 16 ( x^2 +14x -2 ) = log 4 (x^2 +14x -2) /
log 4 16


                                           = log 4
(x^2 +14x -2) / log 4
4^2


                                           =  log 4
(x^2 +14x -2) / 2log 4 4


But log 4 (4) =
1


==> log 16 (x^2 +14x -2) = (1/2) log 4 (x^2 +14x
-2)


Now we will substitute into the
equation.


==> (1/2) log 4 (x^2 +14x -2) = log 4
(x-1)


==> log 4 (x^2 +14x -2)^1/2 = log 4
(x-1)


Now that the logs are equal, then the bases are
equal.


==> (x^2 +14x -2)^1/2 =
x-1


We will square both
sides.


==> x^2 +14x -2 = x^2 -2x +
1


We will reduce
similar.


==> 14x -2 = -2x
+1


We will combine like
terms.


==> 16x =
3


==> x =
3/16

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