Practicing Success
Practicing Success
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If A is a square matrix such that $A^2 = 2I$, then the value of $(A - I)^2 + (A+I)^2-7A$ is |
$2I$ $-7A+6I$ $-8I-7A$ $8I+7A$ |
$-7A+6I$ |
$A^2 = 2I$ so $(A-I)^2+(A+I)^2-7A$ $A^2+I-2A+A^2+I+2A-7A$ $=2A^2+2I-7A$ $4I+2I-7A$ $[∵A^2 = 2I]$ $=-7A+6I$ |
