Subtracting a negative number is the same as adding a positive number. When you see a subtraction sign immediately followed by a negative sign, they effectively cancel each other out, resulting in addition. According to the reference, the two signs (minus and minus) result in a plus sign and the second number will be added to the first.
Here's a more detailed explanation with examples:
Understanding the Concept
Think of a number line. Subtracting a number moves you to the left on the number line. Subtracting a negative number, therefore, moves you opposite to the left, which means you move to the right.
Examples
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Example 1: 5 - (-3)
- The two negative signs become a plus sign: 5 + 3
- Therefore, 5 - (-3) = 5 + 3 = 8
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Example 2: -2 - (-7)
- The two negative signs become a plus sign: -2 + 7
- Therefore, -2 - (-7) = -2 + 7 = 5
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Example 3: 0 - (-4)
- The two negative signs become a plus sign: 0 + 4
- Therefore, 0 - (-4) = 0 + 4 = 4
Rule Summary
The rule to remember is:
| Operation | Result | Explanation |
|---|---|---|
| a - (-b) | a + b | Subtracting a negative 'b' is equivalent to adding the positive version of 'b' to 'a'. |
| a - (+b) | a - b | Subtracting a positive 'b' is the same as subtracting 'b' from 'a'. |
Practical Insight
A common way to remember this is that two negatives make a positive. When you encounter a subtraction sign followed by a negative number in parentheses, immediately change both signs to a single plus sign. This simplifies the equation and makes it easier to solve.
