This question is not very strict. According to the equivalent method.

1=5

Then 5= 1

This is a relatively standard answer.

From another point of view, from the sequence point of view.

1=5

2= 15

3=2 15

4=2 145

5=32345

It's possible, but it's best to answer according to 1 The answer is not necessarily the most important, but the way to solve the problem.