# Finding elementary matrices to complete a set of matrix equations

#### sktsasus

##### New member

I have 89% of the values correct but I'm not sure where I'm going wrong exactly.

For the first ones, the first row is being multiplied by 2 and then multiplied by 1/2, so I multiplied the identity matrix's first row by those amounts.

For the second ones, the second and third row are switched for both so I switched the second and third row of the identity matrix for both as well.

For the third ones, the first row is being added to 4 times the second row and -4 times the second row. So I switched the the first and second row of the identity matrix and multiplied it by 4 and -4 respectively. I have a feeling that this is where I'm going wrong but I'm not sure why.

Any help?

#### stapel

##### Super Moderator
Staff member
View attachment 9094
I have 89% of the values correct but I'm not sure where I'm going wrong exactly.
I'm not sure what you mean by this...? Also, your image is too small, so I can't see what's going on. What was the original exercise? What were the instructions? What are you trying to do?

For the first ones, the first row is being multiplied by 2 and then multiplied by 1/2, so I multiplied the identity matrix's first row by those amounts.

For the second ones, the second and third row are switched for both so I switched the second and third row of the identity matrix for both as well.

For the third ones, the first row is being added to 4 times the second row and -4 times the second row. So I switched the the first and second row of the identity matrix and multiplied it by 4 and -4 respectively. I have a feeling that this is where I'm going wrong but I'm not sure why.
Were you perhaps given a matrix? And were the instructions perhaps to reduce the matrix in some way? Are you perhaps supposed to be using row operations? Do the above sentences refer to row operations? If so, then what do you mean when you, for instance, say that you multiplied the first row by 2 and then 1/2 (which of course leaves the row unchanged)?