1. Calculate: $123456789 \times 8+9=$
Solution: 987654321.
Starting from 1, the $n$-digit number that increases by one each time, when multiplied by 8 and then adding $n$, results in an $n$-digit number that starts from 9 and decreases by one each time.
$$
123456789 \times 8+9=987654321
$$