Prove or disprove that a 4 x 4 board with any one square removed can be tiled with pieces consisting of three squares in an L-shape. Prove or disprove that an 8 x 8 board with any one square removed can be tiled with pieces consisting of three squares in an L-shape. Determine if ((pq)) ^ ( (qp)) is a tautology, a contradiction or neither. Use the gcd reduction theorem (the Euclidean algorithm) to nd the great- est common divisor of 7854 and 4746. Find [8842 (-4940)20] (mod 7).