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).
Last edited by DarK; Oct 24th 2010 at 08:37 AM.
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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.
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 $\displaystyle A(A+ I_n)= (A+ I_n)A= I_n$.
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