Rules for adding and subtracting positive and negative numbers
When two signs are written next to each other, the rules for adding and subtracting numbers are:
- two signs that are different become a negative sign
- two signs that are the same become a positive sign
Examples
- Same signs give a positive: \(3 + (+2) = 3 + 2 = 5\)
- Same signs give a positive: \(3 - (-2) = 3 + 2 = 5\)
- Different signs give a negative: \(3 + (-2) = 3 - 2 = 1\)
- Different signs give a negative: \(3 - (+2) = 3 - 2 = 1\)
Question
Calculate \(-5 + (-4)\).
\(-5 + (-4) = -5 - 4 = -9\)
Question
Calculate \(-1 - (-7)\).
\(-1 - (-7) = -1 + 7 = 6\)
Question
Calculate: \(- 2 + 9 - 10 + 6\).
The answer is \({3}\) or \({+3}\).