Which of the following functions is continuous for all real numbers?
f(x)=x3−2x+7f(x) = x^3 - 2x + 7f(x)=x3−2x+7
f(x)=1x2+1f(x) = \frac{1}{x^2 + 1}f(x)=x2+11
f(x)=xx−3f(x) = \frac{x}{x-3}f(x)=x−3x
Both (a) and (b)