If A=$\begin{bmatrix}3 & 2\\1 & 1\end{bmatrix}$ find the values of a and b, such that $A^2+aA+bI=0.$
$\begin{array}{1 1}(A)\;a=4,b=-1\\(B)\;a=-1,b=4\\(C)\;a=-1,b=-4\\(D)\;a=-4,b=1\end{array}$