Look at the pattern: 3 × (−4) = −12, 2 × (−4) = −8, 1 × (−4) = −4, 0 × (−4) = 0. Continuing the same pattern, what is (−1) × (−4)?

Each time the first factor drops by 1, the product climbs by 4: −12 → −8 → −4 → 0. The next step gives 0 + 4 = 4, so (−1) × (−4) = 4. This is how the 'two negatives make a positive' rule is discovered — it keeps the pattern unbroken. Choosing −4 keeps subtracting instead of noticing the products are rising.