Newton's algorithm for a polynomial of arbitary degree
In general, LGTM. Few notes:


The name f is meaningless. newtonDelta perhaps?
It feels right to compute a derivative's coefficients once, and reuse evalPoly for both the function and its derivative. After all, the polynomial's derivative is also polynomial. There is an usual space-time tradeoff, but in the case of polynomials DRY rule casts a deciding vote.
Newton's algorithm does not necessarily converge. You should be prepared to handle the divergent case.
Hardcoding ε is dubious. I recommend to solveNewton have it as a parameter.
Using Horner schedule is a definite improvement.