Pre Calc Help D:

Actually it only needs to be in "Reduced Row Echelon" form.

• All nonzero rows are above any rows of all zeroes.
• The leading coefficient (also called pivot) of a row is always strictly to the right of the leading coefficient of the row above it.
• Every leading coefficient is 1 and is the only nonzero entry in its column.
  

In the matrix:

| 1 0 -3 -10|
| 0 1 3 34|
| 0 0 0 0 |

the threes in column three just signify that it's a free variable. You can define the set of equations being represented by the matrix as a 1-parameter family of solutions, or a line in 3-space dimension.

Of course, an Identity matrix means there's only 1 solution, which is preferred =P But if you have the Reduced Row Echelon form of a matrix, and it's not an Identity matrix, then it has infinite solutions instead.

I know what REF is, I've taken Linear Algebra, and even though I completely failed at it, I haven't forgotten how to do that

He said RREF, so I was being technical D: