4. 9 × 81 (1 point)
(9 × 80) + 1 = 7211
(9 × 80) + (9 × 1) =729
(9 × 90) – (9 x 1) = 801
(9 × 80) – (9 × 1) 711
(9 × 80) + (9 × 1) =729
(9 × 80) + 1 = 7211
(9 × 80) + (9 × 1) =729
(9 × 90) – (9 x 1) = 801
(9 × 80) – (9 × 1) 711
(9 × 80) + (9 × 1) =729