Which of the following functions has a domain of x≥0x \geq 0x≥0?
f(x)=x2f(x) = x^2f(x)=x2
f(x)=xf(x) = \sqrt{x}f(x)=x
f(x)=∣x∣f(x) = |x|f(x)=∣x∣
f(x)=3x−1f(x) = 3x - 1f(x)=3x−1