To find the intervals on which f(x) is concave up/down, we need to calculate the second derivative of f(x):
f(x) = 1/2x^2 + 3
f'(x) = x
f''(x) = 1
Since f''(x) is positive for all x, f(x) is always concave up.
To find the inflection points of f(x), we need to solve the equation f''(x) = 0. However, since f''(x) is a constant function, it never equals zero. Therefore, f(x) has no inflection points.
In summary, the function f(x) = 1/2x^2 + 3 is always concave up and has no inflection points.