For each function $f(x,y,z)$, determine whether its gradient points radially outward from the origin, radially inward toward the origin, radially outward from the z-axis, or radially inward toward the z-axis.

? Points radially outward from the origin Points radially inward toward the origin Points radially outward from the z-axis Points radially inward toward the z-axis  1. $f(x,y,z) = x^2 + y^2 + z^2$

? Points radially outward from the origin Points radially inward toward the origin Points radially outward from the z-axis Points radially inward toward the z-axis  2. $f(x,y,z) = x^2 + y^2$

? Points radially outward from the origin Points radially inward toward the origin Points radially outward from the z-axis Points radially inward toward the z-axis  3. $\displaystyle f(x,y,z) = \frac{1}{x^2 + y^2 + z^2}$

? Points radially outward from the origin Points radially inward toward the origin Points radially outward from the z-axis Points radially inward toward the z-axis  4. $\displaystyle f(x,y,z) = \frac{1}{x^2 + y^2}$