Answers:
- 7. D
- 8. C
- 9. D
- 10. D
- 11. C
- 12. B
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Step-by-step explanation:
The result of problem 7 is undefined because the matrices are not the same size. Both matrices must have the same number of rows, and they must have the same number of columns. This is so the terms match up when we add them. This applies to question 9 as well because subtraction is a form of addition.
For problem 8, we add the corresponding terms. So for instance, along the top we have -2+(-3) = -5 as the first entry in the top row. So that's why the answer is C for problem 8. Problem 10 and 11 are similar to this. Be careful to distribute the negative through to each term in the second matrix when subtracting matrices.
For problem 12, we multiply the outer 3 by each term inside the matrix. We end up with choice B.