If \(a^2 + b^2 + c^2 + ab + bc + ca \leq 0\), where \(a, b, c \in R\) and \(f(x) = a[x] + b|x| + c\,\text{sgn}(x)\), then in \((-2, 2)\), which of the following is not true?[Note: \([y]\) denotes greatest integer function less than or equal to \(y\).]