Each of the following functions has domain x∈Rx \in \mathbb{R}x∈R.
Which function does not have an inverse function?
f(x)=5x−2f(x) = 5x - 2f(x)=5x−2
f(x)=x3+4f(x) = x^3 + 4f(x)=x3+4
f(x)=cos(x)f(x) = \cos(x)f(x)=cos(x)
f(x)=2xf(x) = 2^xf(x)=2x
