Math Help - NullSpace

Let S be the subspace of R4 given by the solution set of the equations
-x3 + 4 x4 = -x2 - x3 + x4 and -x1 - x3 = -x1 - 3 x3 = x2

An example of a matrix for which S is the nullspace is....

i tried doing 1 1 0 0
0 1 0 3

Originally Posted by ah-bee

Let S be the subspace of R4 given by the solution set of the equations
-x3 + 4 x4 = -x2 - x3 + x4 and -x1 - x3 = -x1 - 3 x3 = x2

An example of a matrix for which S is the nullspace is....

i tried doing 1 1 0 0
0 1 0 3

.... (1)

.... (2)

.... (3)
Substitute from (1) and (2): .

So elements of S have the form .

So the example you propose works.

the problem is.. when i enter my solution into the web page (online assignment), it says that it is wrong. any ideas why?

Originally Posted by ah-bee

the problem is.. when i enter my solution into the web page (online assignment), it says that it is wrong. any ideas why?

1. Perhaps a 4x4 matrix is wanted ....? In which case the question should be more specific on the dimension required.

2. Have you correctly copied the system of equations?

1. I gave a 2x4 matrix in a similar practice question and got it right + there are no specific matrix dimensions required.

2. Yeah, I've copied the equations down correctly.