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sqrt(x-1)=x

Solution? How many?

 May 16, 2016
 #1
avatar+9676 
0

\(\sqrt{x-1}=x\)

\(x-1=x^2\)

\(x^2-x+1=0\)

\(x=\frac{(-1)^2\pm\sqrt{4(1)(1)}}{2(1)}\)<------ Quadratic Equation

\(= \frac{1}{2}\pm\frac{2}{2}\)

x = 3/2 or x=-1/2

There are two solutions.

 May 16, 2016
 #2
avatar+33661 
0

You should check your results Max!  

 

You haven't done the quadratic solution correctly.

 May 16, 2016
 #3
avatar+9676 
0

Oops. I was wrong

\(\sqrt{x-1}=x\)

\(x-1=x^2\)

\(x^2-x+1=0\)

\(x=\frac{-(-1)\pm\sqrt{(-1)^2-4(1)(1)}}{2(1)}\)<------ Quadratic Equation

=\(\frac{1}{2}\pm\frac{\sqrt{-3}}{2}\)

=\(\frac{1\pm\sqrt3i}{2}\)

No real roots and 2 imaginary roots

 May 16, 2016
 #4
avatar
0

Solve for x:
sqrt(x-1) = x

 

Raise both sides to the power of two:
x-1 = x^2

 

Subtract x^2 from both sides:
-x^2+x-1 = 0

 

Multiply both sides by -1:
x^2-x+1 = 0

 

Subtract 1 from both sides:
x^2-x = -1

 

Add 1/4 to both sides:
x^2-x+1/4 = -3/4

 

Write the left hand side as a square:
(x-1/2)^2 = -3/4

 

Take the square root of both sides:
x-1/2 = (i sqrt(3))/2 or x-1/2 = 1/2 (-i) sqrt(3)

 

Add 1/2 to both sides:
x = 1/2+(i sqrt(3))/2 or x-1/2 = 1/2 (-i) sqrt(3)

 

Add 1/2 to both sides:
Answer: |  x = 1/2+(i sqrt(3))/2     or      x = 1/2-(i sqrt(3))/2

 May 16, 2016

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