Algebra - Substitution
"Substitute" means to put in the place of another.
Substitution
In Algebra "Substitution" means putting numbers where the letters are:
When we have: |
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And we know that x=6 ... | |||||||
... then we can "substitute" 6 for x: |
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As that last example showed, we may not always get a number for an answer, sometimes just a simpler formula.
Negative Numbers
When substituting negative numbers, put () around them so you get the calculations right.
In that last example:
- the − (−2) became +2
- the (−2)2 became +4
because of these special rules:
Rule | Adding or Subtracting | Multiplying or Dividing | ||
---|---|---|---|---|
Two like signs become a positive sign | 3+(+2) = 3 + 2 = 5 | 3 × 2 = 6 | ||
6−(−3) = 6 + 3 = 9 | (−3) × (−2) = 6 | |||
Two unlike signs become a negative sign | 7+(−2) = 7 − 2 = 5 | 3 × (−2) = −6 | ||
8−(+2) = 8 − 2 = 6 | (−3) × 2 = −6 |
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