a)$y=x^3+3mx^2+(3m^2+m+1)x+5m$
$y' = 3x^2 + 6mx + 3m^2+m+1 \geq 0 \forall x \in R \\ \\ 3 > 0 \Rightarrow \Delta' = 9m^2- 3(3m^2+m+1) \leq 0 \\ \\ \Rightarrow m \geq -1 $
b)$y=mx^3+3x^2+(2m-1)x-m$
$y' = 3mx^2 + 6x + 2m-1 \geq 0 \forall x \in R \\ \\ \begin{cases} m > 0 \\ \Delta' \leq 0 \end{cases}$