$$\lim_{x \to \infty}\left(n x \left(n + x\right)\right) = \infty \operatorname{sign}{\left(n \right)}$$
$$\lim_{x \to 0^-}\left(n x \left(n + x\right)\right) = 0$$
More at x→0 from the left$$\lim_{x \to 0^+}\left(n x \left(n + x\right)\right) = 0$$
More at x→0 from the right$$\lim_{x \to 1^-}\left(n x \left(n + x\right)\right) = n^{2} + n$$
More at x→1 from the left$$\lim_{x \to 1^+}\left(n x \left(n + x\right)\right) = n^{2} + n$$
More at x→1 from the right$$\lim_{x \to -\infty}\left(n x \left(n + x\right)\right) = \infty \operatorname{sign}{\left(n \right)}$$
More at x→-oo