Thursday, February 25, 2010

`x^2 - x = log_5(25)` Solve for x or b

`x^2-x=log_5 (25)`


First, simplify the right side of the equation. To do so, factor 25.


`x^2 - x = log_5 (5^2)`


Then, apply the logarithm rule `log_b (a^m) = m * log_b (a)` .


`x^2 - x = 2 * log_5 (5)`


Take note that when the base and argument of the logarithm are the same, its resulting value is 1 `(log_b (b)=1)` .


`x^2 - x = 2 * 1`


`x^2 - x = 2`


To solve quadratic equation, one side should be zero.


`x^2 - x -2 =0`


Then, factor the left side.


`(x - 2)(x + 1)=0`


Set each factor equal to zero. And isolate the x.


`x - 2 = 0`


`x=2`



`x + 1=0`


`x=-1`



Therefore, the solution is `x = {-1,2}` . 

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