Saturday, June 8, 2013

sqrt( x^2 - 5x + 4 ) = sqrt( x^2 + 3x -2) find x.

We'll impose the constraint of existence of square
roots:


 x^2 - 5x + 4>=0


We'll
re-write the
inequality:


(x-1)(x-4)>=0


The
intervals of admissible values are (-infinte ,1)U(4 ,
+infinite).


x^2 + 3x -2>=0


x1 =
[-3+sqrt(9+8)]/2


x1 = (-3+sqrt17)/2


x2
= (-3+sqrt17)/2


The intervals of admissible values are (-infinte
,(-3+sqrt17)/2)U((-3+sqrt17)/2 , +infinite).


The solution of the
equation has to belong to the intervals of admissible
values:


(-infinte ,(-3+sqrt17)/2)U(4 ,
+infinite).


Now, we can solve the equation by raising to square both
sides, to get rid of the square roots:


( x^2 - 5x + 4 ) = ( x^2 + 3x
-2)


We'll eliminate and combine like
terms:


-5x - 3x + 4 + 2 = 0


-8x + 6 =
0


-8x = -6


x =
6/8


x = 3/4


We notice
that the value for x doesn't belong to the interval of admissible values for x, so the equation
has no solution.

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