AA' A = A
(AA')2 = A
AA'A = $$I$$
AA'A = A'
Answer is Wrong!
Answer is Right!
The correct answer is $\boxed{\text{C}}$.
Let $A$ be an $m\times n$ full rank matrix with $m>n$. Then, $A^T A$ is an invertible matrix. Therefore, $(A^T A)^{-1}$ exists.
We know that $A^T A A = A^T$. Therefore,
\begin{align}
AA’ 213.4-11.5c23.5-6.3 42-24.2 48.3-47.8 11.4-42.9 11.4-132.3 11.4-132.3s0-89.4-11.4-132.3zm-317.5 213.5V175.2l142.7 81.2-142.7 81.2z"/>
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