Thursday, September 25, 2014

Solve the equation log(2) [x(x-1)]=1

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


x(x-1)>0


The
range of admissible values for x is (1 ; +infinite).


We'll
solve the equation by taking anti-logarithm:


x(x-1) =
2^1


We'll remove the
brackets:


x^2 - x - 2 =
0


We'll apply quadratic
formula:


x1 = [1 + sqrt(1 +
8)]/2


x1 = (1+3)/2


x1 =
2


x2 = -1


Since the second
value of x doesn't belong to (-1; +infinite), we'll reject
it.


We'll accept as solution of equation x =
2.

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