Negative numbers in everyday life and AI

The number line extends in both directions:

… −5  −4  −3  −2  −1   0   1   2   3   4   5 …

Negative numbers are common in the workplace: a minus degree in the weather forecast, a deficit of 200 SEK in the cash register, or a delay of three hours.

The rule that helps: plus = move right, minus = move left.

• 3 − 5: start at 3, move 5 steps left → −2.
• −2 + 6: start at −2, move 6 steps right → 4.
• −2 − 3: start at −2, move 3 steps left → −5.

A minus before a minus becomes a plus: 5 − (−3) = 5 + 3 = 8. Think of it as “removing a debt of 3” — you become 3 units richer.

Multiplication and division:

• (+) · (+) = + and (−) · (−) = +
• (+) · (−) = − and (−) · (+) = −

So (−4) · (−2) = 8 and (−4) · 2 = −8.

In AI, negative numbers appear directly: gradients are negative when you need to adjust upwards, weights can be negative (meaning they counteract a pattern), and error margins can be below zero.