For matrix addition $A+B$ to be defined, which condition must hold?
A$A$ and $B$ must both be square
BNumber of rows of $A$ must equal number of columns of $B$
C$A$ and $B$ must be of the same order
DThe determinant of each matrix must exist
Answer & Solution
Correct answer: C. $A$ and $B$ must be of the same order
Matrix addition is defined only when corresponding entries can be added, so the two matrices must have the same order. Being square is not necessary, and determinant is irrelevant for addition.
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