Definite integral involving nested square root.

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If$y=\sqrt{(x^2+x+1)+\sqrt{(x^2+x+1)-\sqrt{(x^2+x+1)+\sqrt{(x^2+x+1)\cdots\cdots}}}}$. Then $\displaystyle \int^{3}_{2}ydx$.

Try: writting equation as $$y=\sqrt{(x^2+x+1)+\sqrt{(x^2+x+1)-y}}$$

So $$y^2=x^2+x+1+\sqrt{(x^2+x+1)-y}$$

$$\bigg(y^2-(x^2+x+1)\bigg)^2=(x^2+x+1-y)$$

I did not understand how can i calculate $y$ in terms of $x$

Could some help me to solve it, Thanks

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Squaring the radical equation twice is likely to introduce extraneous functional solutions. The doubly-squared equation is difficult to factor "by hand" but Wolfram factors it as

$$ (x-y+1)(x+y)\left(x^2+x-y^2-y+1\right)=0 $$

giving possible solutions

  1. $y=x+1$
  2. $y=-x$
  3. $\left(x+\frac{1}{2}\right)^2-\left(y+\frac{1}{2}\right)^2=1$ which is an hyperbola with two solutions for $y$.

The solution is $y=x+1$ for $x\ge0$ as can be seen by direct substitution into the original equation

$$y=\sqrt{(x^2+x+1)+\sqrt{(x^2+x+1)-y}} $$

so the integral $\int_2^3y\,dy$ is straightforward.

After squaring twice you get four functional solutions, three of which are extraneous. Here is the graph of the last equation stated in the question.

Graph of last equation