If $f(x)=(x+1)^2-1, x \geq-1$, then $\left\{x \mid f(x)=f^{-1}(x)\right\}$ is

$$ \text { Consider the following statements. } $$

$$ \begin{array}{cl} \hline \text { Statement I } & \begin{array}{l} \text { A function } f: A \rightarrow B \text { is said to be one-one if and } \\ \text { only if } f(x) \neq f(y) \Rightarrow x \neq y \end{array} \\ \hline \text { Statement II } & \begin{array}{l} \text { A relation } f: A \rightarrow B \text { is said to be a function if } x \neq y \\ \Rightarrow f(x) \neq f(y) \end{array} \\ \hline \end{array} $$

Then, which one of the following is true?

The set of all real values of $x$ for which $f(x)=\sqrt{\frac{|x|-2}{|x|-3}}$ is a well defined function is

Let $f: N \rightarrow N$ be a function such that $f(x+y)=f(x)+f(y)+x y$ for every $x, y \in N$. If $f(\mathbb{l})=2$, then $\sum_{k=0}^{10} f(k)=$