Monday, June 29, 2015

log(x+1) (x^2+3x-14)=2

Supposing that x + 1 is the base of logarithm, we'll
impose the constraints of existence of logarithms:


x+ 1
>0


x + 1different from
1


x different from
0


x>-1


x^2+3x-14
> 0


x^2+3x-14 = 0


x1 =
[-3+sqrt(9 + 56)]/2


x1 = (-3 +
sqrt65)/2


The range of admissible values of x for the
logarithms to exists, is: ((-3 + sqrt65)/2 ;
+infinitte).


We'll solve the
equation:


x^2+3x-14 =
(x+1)^2


We'll expand the square from the right
side:


x^2+3x-14 = x^2 + 2x +
1


We'll eliminate x^2:


3x-14 =
2x + 1


We'll subtract 2x + 1 both
side:


3x - 2x - 14 - 1 = 0


x -
15 = 0


x =
15


Since the value of x belongs to the
interval of admissible values, we'll accept as solution of the equation x =
15.

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