$$\lim_{x \to \infty} \left(x^{2} + y^{2}\right)^{2} = \infty$$ $$\lim_{x \to 0^-} \left(x^{2} + y^{2}\right)^{2} = y^{4}$$ More at x→0 from the left $$\lim_{x \to 0^+} \left(x^{2} + y^{2}\right)^{2} = y^{4}$$ More at x→0 from the right $$\lim_{x \to 1^-} \left(x^{2} + y^{2}\right)^{2} = y^{4} + 2 y^{2} + 1$$ More at x→1 from the left $$\lim_{x \to 1^+} \left(x^{2} + y^{2}\right)^{2} = y^{4} + 2 y^{2} + 1$$ More at x→1 from the right $$\lim_{x \to -\infty} \left(x^{2} + y^{2}\right)^{2} = \infty$$ More at x→-oo