I have no idea where to begin, if someone could help me get started.

Also, I'm a little unsure about what to do for the first question as well (part a).

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- Apr 14th 2010, 03:56 PMDarKWrite the inverse of A in terms of the matrix A
I have no idea where to begin, if someone could help me get started.

Also, I'm a little unsure about what to do for the first question as well (part a). - Apr 14th 2010, 04:04 PMdwsmith
Matrix multiplication general isn't commutative.

$\displaystyle (A-B)(A+B)=A^2+AB-BA-B^2$

If $\displaystyle AB \neq BA$, then $\displaystyle AB-BA$ isn't guaranteed to equal to 0. - Apr 15th 2010, 06:00 AMHallsofIvy
You titled this "write the inverse of A in terms of the matrix A" but then didn't ask about (b)!

If $\displaystyle A^2+ A- I_n= 0$ then $\displaystyle A(A+ I_n)= (A+ I_n)A= I_n$.