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Determinants

Level 13 / realistic untimed

3x3 sparse (+/-6)

3 visual steps / sparse cofactor expansion

1. Sparse line

1. Sparse linechoose column 2.402356105choose column 25 x (20 - 2)det = 90
choose column 2.

choose column 2.

2. Live minor

2. Live minor5 x (20 - 2).402356105choose column 25 x (20 - 2)det = 90
5 x (20 - 2).

5 x (20 - 2).

3. Determinant

3. Determinantdet = 90.DeterminantSettle signed terms.det = 90.5 x (20 - 2)
det = 90.

det = 90.

Practice Level 13

A few quick rounds make the products familiar; the sign is the only thing to guard.

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