SOLUTION: Find all the real solution of the equation x^2-|x-1|-3=0

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Question 1031664: Find all the real solution of the equation
x^2-|x-1|-3=0

Found 2 solutions by ikleyn, Fombitz:
Answer by ikleyn(52787) About Me  (Show Source):
You can put this solution on YOUR website!
.
Find all the real solution of the equation
x^2-|x-1|-3=0
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

x%5E2+-+abs%28x-1%29+-+3 = 0.       (1)

1. Consider the domain x >= 1.
   In this domain |x-1| = x-1,
   and yours equation (1) becomes

   x%5E2+-+%28x-1%29+-+3 = 0,  or

   x%5E2+-+x+-+2 = 0,

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

   with the roots x = 2 and x = -1.

   Of them, only x = 2 belongs to the domain x >= 1.
   So, x = 2 is the ONLY solution of the equation (1) in this domain.


2. Next, consider the domain x < 1.
   In this domain |x-1| = -(x-1). 
   and yours equation (1) becomes

   x%5E2+-+%28-%28x-1%29%29+-+3 = 0,  or

   x%5E2+%2B+x+-+4 = 0.

   Find the roots using the quadratic formula.

   x%5B1%5D = %28-1+%2B+sqrt+%2817%29%29%2F2,  x%5B2%5D = %28-1+-+sqrt+%2817%29%29%2F2.

   Of them, only x%5B2%5D = %28-1+-+sqrt+%2817%29%29%2F2 belongs to the domain x < 1.

   So, x%5B2%5D = %28-1+-+sqrt+%2817%29%29%2F2  is the ONLY solution of the equation (1) in this domain.

Answer.  The solutions are  x = 2  and  x = %28-1+-+sqrt+%2817%29%29%2F2.


Answer by Fombitz(32388) About Me  (Show Source):
You can put this solution on YOUR website!
abs%28x-1%29=x-1 when x-1%3E=0 or x%3E=1
abs%28x-1%29=-%28x-1%29=-x%2B1 when x-1%3C0 or x%3C1
So then,
when x%3E=1
x%5E2-%28x-1%29-3=0
x%5E2-x%2B1-3=0
x%5E2-x-2=0
%28x-2%29%28x%2B1%29=0
Only one factor is in the range,
x-2=0
highlight%28x=2%29
and when x%3C1
x%5E2-%28-x%2B1%29-3=0
x%5E2%2Bx-4=0
%28x%5E2%2Bx%2B1%2F4%29-4-1%2F4=0
%28x%2B1%2F2%29%5E2=17%2F4
x%2B1%2F2=0+%2B-+sqrt%2817%29%2F2
x=-1%2F2+%2B-+sqrt%2817%29%2F2
Again only one factor is in the range,
x=-1%2F2+-+sqrt%2817%29%2F2
highlight%28x=-%28%281%2Bsqrt%2817%29%29%29%2F2%29
.