deletions | additions       diff --git a/bits4.tex b/bits4.tex  index 4f9dd4a..702d6ff 100644  --- a/bits4.tex  +++ b/bits4.tex 
...
We are interested in a function that returns $1$ if a vector of bits is null, $0$ otherwise.  This is extremely useful Boolean function, since it recognizes if a vector of bits is the null vector $(0,\ldots,0)$. \\  We now show how to obtain a polynomial representing this function.\\  We observed in exercise \ref{XorIsNice} that the multiplication of bits has the same truth table of the $\AND$ operator. In particular we have $1$ if each bit is $1$, $0$ otherwise. This is the opposite what we want and so we ca add $1$ to have the sought-after function (see exercise  \ref{Not}). If For example, if  $n=3$ we have where $z(x,y,z)=xyz+1$. the function is $(x,y,z) \mapsto xyz+1$.  \end{Example}