Systems Of Equations Math Worksheet (Page 3 of 3) in pdf

Systems Of Equations Math Worksheet Page 3

Elimination

Elimination involves eliminating either the “x” or “y” variable out of both

equations so the other can be solved for. Before we get into that, let’s examine a

few true number sentences. We’re going to add these equations up and down to

see if we get another true statement.

Try it with some negatives! Æ

2 + 9 = 11

-9 + 2 = -7

3 + 5 = 8

-2 – 12 = -14

Adding up and down gives us another true statement! So, this is the idea we are

going to use for variables.

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Ex 4:

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So, add these up and down. Notice how the “y” value

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cancels out completely. Take the value we got for “x”

and now plug it into one of the original two equations.

Then, solve for “y”.

2(_____) + y = 5

We can use this method for checking out example 3.

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The thing here is that if we just add, then nothing will cancel

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out! We’ll get 6x – 9x = 24. So, before we go any further, we

need to multiply either the top or the bottom equation by

something that will make one of the variables cancel. Let’s

multiply the top equation by -2. Doing so, will make the “x”s

cancel: -2(2x – 3y = 8) Æ -4x + 6y = -16

-4x + 6y = -16

So, here is what we now have. We can add these

4x – 6y = 16

now! See how everything cancels out? That means

these are the same line.

Systems Of Equations Math Worksheet Page 3