Which of these functions has a restricted 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)=2x+1f(x) = 2x + 1f(x)=2x+1