Question 1126696
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The first statement in each pair is a meaningful matrix equation, showing the sum of two matrices being equal to a third matrix.  That makes problems 1 and 4 easy to solve; your answers are correct.<br>
The second statement in each pair has no meaning.  What is it supposed to mean when you write three matrices next to each other, with no operations between the matrices, and without an equals sign?  So questions 2 and 5 can't be answered.<br>
For question 3, there is nothing in the given information about matrix A; how can we tell what element a12 is?