Answer:
A). Alberto is the only right one because .80 * 5 = 4$
B). Claude will need 1.60$ because .80 * 2 = 1.60$
C). Dora can buy 12.5 pounds because 10$ / .80 is 12.5
D). Using Alberto's because he was the one who was correct
Step-by-step explanation:
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Answer:
C
Step-by-step explanation:
15. B: If 
is non-zero, then 
. We have
so
16. C: In general, 
for two matrices 
, but equality holds if 
. D is incorrect because 
.
17. C: This follows from a property of the determinant:
where 
is the size of the (square) matrix 
(and "size" refers to the number of rows or columns, both of which are the same).
18. A: A matrix has no inverse if its determinant is 0. The determinant of (A) is 0 because it contains a row made up entirely of 0s.
19. B: The matrix product 
only exists if the number of columns of 
is equal to the number of rows of . In (a), the first matrix has 1 column and the other has 2 rows, so multiplication is invalid. In (c), the product on the left side would produce
so that 
and 
, but these values don't work with the given equations because -45 - 3(29) = -132, not -3. In (d), the product on the left side is
but then this would mean both 
and 
, which are not consistent and have no solution.
