A=matrix([[-1,1,2],[3,-1,1],[-1,3,4]])
A_11=det(matrix([[-1,1],[3,4]]))
A_21=det(matrix([[-1,-2],[-3,-4]]))
A_31=det(matrix([[1,2],[-1,1]]))
A_12=det(matrix([[-3,-1],[1,-4]]))
A_22=det(matrix([[-1,2],[-1,4]]))
A_32=det(matrix([[1,-2],[-3,-1]]))
A_13=det(matrix([[3,-1],[-1,3]]))
A_23=det(matrix([[1,-1],[1,-3]]))
A_33=det(matrix([[-1,1],[3,-1]]))
B=matrix([[A_11,A_21,A_31],[A_12,A_22,A_32],[A_13,A_23,A_33]])
D=det(A)
A_inv=B/D
print(A_inv)