All Linear Algebra Resources
Example Questions
Example Question #11 : Linear Equations
Example Question #12 : Linear Equations
Example Question #13 : Linear Equations
Example Question #14 : Linear Equations
Example Question #15 : Linear Equations
Example Question #16 : Linear Equations
Example Question #17 : Linear Equations
Example Question #18 : Linear Equations
Give the elementary matrix that represents performing the row operation
in solving a three-by-three linear system.
The elementary matrix that represents a row operation is the result of performing the same operation on the appropriate identity matrix - which here is the three-by-three matrix . The row operation is the multiplication of each element of in the second row of an augmented matrix by the scalar , so do this to the identity:
This is the correct response.
Example Question #11 : Reduced Row Echelon Form And Row Operations
Which of the following is an example of an elementary matrix?
An elementary matrix is one that can be formed from the (here, three-by-three) identity matrix
by way of exactly one row operation. An elementary matrix can have one of the following characteristics:
1) Exactly two rows are switched. The only choice that repositions rows is
,
but this choice rearranges all three rows, so this is incorrect.
2) All of the "1" elements in the diagonal remain unchanged, but exactly one "0" is changed to a nonzero number. The choice that leaves all "1" elements unchanged is
but this matrix changes two of the zeroes to nonzero elements.
3) One of the "1" elements in the diagonal is changed to another nonzero element. The other three choices change these elements. But, of them:
changes two of the "1" elements to other nonzero numbers, and
also changes a "0" to a nonzero number.
,
however, makes one such change and no others, so it is an elementary matrix, and it is the correct choice.
Example Question #20 : Reduced Row Echelon Form And Row Operations
Which of the following elementary matrices represents the row operation
on a four-by-four system?
None of the other choices gives the correct response.
An elementary matrix is one that can be formed from the (here, four-by-four) identity matrix
by way of exactly one row operation. represents the addition of times each element in Row 1 to the corresponding element in Row 4, so do this in the identity matrix:
,
the correct choice.