2a 2 5b 2 9c 2 4ab 2b 6ac 1 0 July 8, 2019 16 32 64 128 2) 5ac - 6bd + 5ad - 6bc 4) 4ab - 6cd - 12ad + 2bc 2 4(8a-9b)-4 1(5b+6c)-1 9(-4a+7c)
