Tính nhanh: \[{\rm{A}} = \left( {\frac{1}{4} - 1} \right).\left( {\frac{1}{9} - 1} \right).\left( {\frac{1} - 1} \right).\left( {\frac{1} - 1} \right).....\left( {\frac{1} - 1} \right).\]