Let be the set of all polynomial functions of degree 4 or less on . If and , we define .
Further, we define .
Will be a complete metric space?
Since is finite dimensional and is a norm it follows that is a Banach space.
If is a Cauchy sequence in , then for there exist such that for . A direct calculation shows that this implies
Taking small enough (the quotient in the last inequality goes to 0 as goes to 0), this shows that is a Cauchy sequence in . Hence there
such that tends to in . But this implies that tends to in , since
Thus the answer is yes if you show that is actually a metric.
The completenes of follow from the given argument above, Cauchy in implies Cauchy in , then convergence in and .
I believe that in the same book I have mentioned you can find the clues to show that defines a metric.