8-2. On a distant planet in the mangrove forests, there lives a population of frogs. The number of frogs born each year is one more than the difference between the number of frogs born in the previous two years (the larger number minus the smaller number).

For example, if 5 frogs were born last year and 2 in the year before, then 4 frogs will be born this year; if 3 frogs were born last year and 10 in the year before, then 8 frogs will be born this year.

In 2020, 2 frogs were born, and in 2021, 9. In which nearest year will only 1 frog be born for the first time?
Answer: 2033.

Solution: This is a fairly simple problem where the only thing you need to do is correctly understand the condition and apply it the necessary number of times. The ability to correctly understand the condition is an important skill in solving problems!

By applying the algorithm described in the condition, we get that the number of frogs born on the planet is $2 \rightarrow 9 \rightarrow 8 \rightarrow 2 \rightarrow 7 \rightarrow 6 \rightarrow 2 \rightarrow 5 \rightarrow 4 \rightarrow 2 \rightarrow 3 \rightarrow 2 \rightarrow 2 \rightarrow 1$, which means that 12 more years need to pass starting from 2021, hence the answer is 2033.