A positive number x and its reciprocal are added together. The smallest possible value of this sum is obtained by minimizing f(x). The function f(x) and its domain for this problem are …(respectively)
f(x) = x + x^(-2) with the domain (0,∞)
f(x) = x^2 + 1 with the domain (0,∞)
f(x) = x + (1/x) with domain (-∞,∞)
f(x) = x + (1/x) with the domain (0,∞)