When \(a\ne 0\), there are two solutions to \( a^2x+bx+c=0\) and they are \[x=-b\pm {\sqrt{b^2-4ac}\over 2a}.\]

We prove that the duality map \(\langle\,,\rangle:(\ell^\infty,\hbox{weak})\times((\ell^\infty)^*,\hbox{weak}^* )\to {\bf R}\) is not Borel. More generally, the evaluation \(e:(C(K),\hbox{weak})\times K\to{\bf R}\) , \(e(f,x) = f(x)\), is not Borel for any function space \(C(K)\) on a compact \(F\)-space. We also show that a non-coincidence of norm-Borel and weak-Borel sets in a function space does not imply that the duality map is non-Borel.