If the 2×2 matrix A has an inverse and (A−2I)(A−4I)=0, then find A+8A−1.
Like so:
Alternatively,
(A−2I)(A−4I)=A2−6A+8I=0,A2+8I=6A,A+8A−1=6I.
Thanks Alan and guest.
I always need reminding about matrices :)
