| When you add two linear equations and a pair of monomials containing the same variable sums to zero, those variables are said to "drop out". Here are some additions of linear equations to demonstrate this. |
| Example # 1 |
3x + 7y = 2 |
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-3x - 2y = 8 |
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| x dropped out |
5y
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= 10
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| Example # 2 |
 -x
+ 4y = -3 |
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 2x
- 4y = 5 |
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| y dropped out |
x
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=2
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To have a variable drop out of this system of equations, two things have to be present in the monomials: |
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1.
They must have the same numerical coefficient. (The number in front
of the variable.)
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2.
They must have opposite signs. (One must be + and the other -)
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