How to determine an estimate for the maximum error committed in the interpolation process?

For example:

x |-35 | -1 | 1

f(x) | -2 | -1 | 0

Using Newton's method I found:

$\displaystyle p_2(x) = 0,5x^2+18,0294x+16,53$

Now what do I need to determine an estimate for the maximum error of interpolation?