Observe each of the following formulas and fill in the blanks according to the rules you find 4*5=20,3*6=18 5*6=30,4*7=28 6*7=42,5*8=40 . If 1222 * 1223 = 1494506, then 1221 * 1224 = () Write the relationship

Observe each of the following formulas and fill in the blanks according to the rules you find 4*5=20,3*6=18 5*6=30,4*7=28 6*7=42,5*8=40 . If 1222 * 1223 = 1494506, then 1221 * 1224 = () Write the relationship

It can be seen from 5 * 6 = 30 and 4 * 7 = 28 that difference = 2
4=5-1,7=6+1
1222*1223=1494506
1221=1222-1
1224=1223+1
So 1221 * 1224 = 1494506-2 = 1494504