Adding two signed integers involves considering their signs. Here's how to do it:
Cases Based on Signs
There are two main cases to consider:
-
Both integers have the same sign:
- Add their absolute values (i.e., treat them as if they were both positive).
- Keep the common sign.
Example:
- (+5) + (+3) = +8 (Both positive, add 5 and 3, keep the positive sign)
- (-5) + (-3) = -8 (Both negative, add 5 and 3, keep the negative sign)
-
The integers have different signs:
- Subtract the smaller absolute value from the larger absolute value.
- Use the sign of the integer with the larger absolute value in the result.
Example:
- (+5) + (-3) = +2 (5 > 3, subtract 3 from 5, keep the positive sign because 5 is positive)
- (-5) + (+3) = -2 (5 > 3, subtract 3 from 5, keep the negative sign because 5 is negative)
Summary Table
Integer 1 Sign | Integer 2 Sign | Operation | Result Sign | Example |
---|---|---|---|---|
Positive | Positive | Add absolute values | Positive | (+4) + (+2) = +6 |
Negative | Negative | Add absolute values | Negative | (-4) + (-2) = -6 |
Positive | Negative | Subtract abs. values | Sign of larger | (+4) + (-2) = +2 |
Negative | Positive | Subtract abs. values | Sign of larger | (-4) + (+2) = -2 |
General Rule
In essence, you are either adding "more of the same" (same sign) or "balancing out" (different signs) with the sign of the larger force winning.