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Coolmath Algebra
Matrices Lesson 2 - Adding and Subtracting (page 1 of 2)
---- This algebra lesson explains how to add and subtract matrices

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This is really easy, but there is one big thing to remember:

THE SIZES MUST BE THE SAME!

Check it out:

Let's add these guys:

[ row 1: 1 , 3 , 4 row 2: -7 , 0 , 5 ] + [ row 1: 6 , -3 , 11 row 2: 0 , 5 , -4 ]

 

We just add the entries in each spot...

[ row 1: 1 + 6 , 3 + ( -3 ) , 4 + 11 row 2: -7 + 0 , 0 + 5 , 5 + ( -4 ) ]


= [ row 1: 7 , 0 , 15 row 2: -7 , 5 , 1 ]

 

That's it!  So, what do ya think -- easiest thing on the whole site?

Here's a subtraction guy -- same idea:

[ row 1: -2 row 2: 0 row 3: 3 row 4: 6 ] - [ row 1: 7 row 2: -8 row 3: 0 row 4: 4 ]
 

                = [ row 1: -2 - 7 row 2: 0 - ( -8 ) row 3: 3 - 0 row 4: 6 - 4 ]         = [ row 1: -9 row 2: 8 row 3: 3 row 4: 2 ]

Notice what's going on with the sizes...  The matrices you add or subtract have to match up!

And the answer is the same size.

Continued on the next page

 The printing and distribution and/or downloading of these lessons is strictly prohibited.
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