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You may or may not have seen this before -- it depends on where you took your last Algebra class.

First, I need to tell you about determinants.  We'll be using these to solve systems.

Say you've got a 2 x 2:

     x - 3y = 4

5x + 7y = 8

We can make something called a "coefficient matrix":

a coefficient matrix ... [ top row: 1 , -3  bottom row: 5 , 7 ]

A matrix is just a grid of numbers with brackets around them.  (Remember that a coefficient is the number in front of the variable...  x = 1x, so the coefficient is 1.)  (We'll learn more about these matrix things in the next chapter.)

We've got rows and columns of the matrix:

[ top row: 1 , -3  bottom row: 5 , 7 ] ... row 1 = 1 , -3 ... row 2 = 5 , 7 ... column 1 = 1 , 5 ... column 2 = -3 , 7