Question

Starting from (−1) × 5, write various products showing some pattern to show (−1) × (−1) =1.

Answer 1

−1 × 5 = −5

−1 × 4 = −4 = − 5 + 1

−1 × 3 = −3 = − 4 + 1

−1 × 2 = −2 = − 3 + 1

−1 × 1 = −1 = − 2 + 1

−1 × 0 = 0 = − 1 + 1

Therefore, −1 × (−1) = 0 + 1 = 1