4)A)

there is $\displaystyle A=\left(\begin{array}{ccc}i & 0 & 1\\0 & 3 & 0\\0 & 0 & i\end{array}\right)$ find polinomial $\displaystyle 0\neq Q(t)=at^{2}+bt+c\in C_{3}[t]$

so $\displaystyle [Q(A)]^{2}=0$

B)there is $\displaystyle A\in M_{nxn}^{F}$ matrices which is not diagonisable.

prove that if F=C (the field is C) then there is a polinomial $\displaystyle 0\neq Q(t)\in C_{n}[t] so [Q(A)]^{2}=0$

c)

does the previos part id true if F=R

?

dont knot from where to start,any starting guidence?