# How many (real) solutions do the equation #abs(x-1) = x^2 + 1# have?

##
- 0
- 1
- 2
- 3
- 4

- 0
- 1
- 2
- 3
- 4

##### 1 Answer

May 17, 2018

#### Answer:

**3.**

#### Explanation:

Given:

#abs(x-1) = x^2+1#

Trying a few small values, we can find solutions:

#abs((color(blue)(0))-1) = 1 = (color(blue)(0))^2+1#

#abs((color(blue)(-1))-1) = 2 = (color(blue)(-1))^2+1#

So it looks like there are

More formally and to check we have not missed any, let's try squaring the given equation to get (for real values of

#x^2-2x+1 = x^4+2x^2+1#

Then subtracting

#0 = x^4+x^2+2x#

#color(white)(0) = x(x^3+x+2)#

#color(white)(0) = x(x+1)(x^2-x+2)#

The remaining quadratic is always positive as we can see by checking its discriminant or by completing the square:

#x^2-x+2 = (x-1/2)^2+7/4#

So it has no factors with real coefficients.