A Karnaugh map provides a pictorial method of grouping together expressions to minimize a given boolean function.
Consider the following function.
F = ∏M (1,2,4,7,11,13).d(9,15)
It is given in terms of maxterms, hence the minimized expression will be in the form of POS. The K-map minimization of the given function is as follows:
Implementation of the above minimized expression using NOR gates is shown below