Answer
The set $W$ of all constant functions: $f(x)=c$ is a vector subspace of $C(-\infty, \infty)$.
Work Step by Step
The set $W$ of all constant functions: $f(x)=c$ is a vector subspace of $C(-\infty, \infty)$. Since the sum of two constant functions is constant and multiplying constant function by a real constant is constant, it is easy to see that $W$ contains the zero and it is closed under addition and scalar multiplication.
