Example 3. How many non-negative integer solutions does the equation have?
Translate the above text into English, please keep the original text's line breaks and format, and output the translation result directly.
Example 3. How many non-negative integer solutions does the equation have?
Translate the above text into English, please keep the original text's line breaks and format, and output the translation result directly.
Let ,
The equation becomes
It is easy to find that (1) has 3 solutions, (2) has 8 solutions.
The original equation has non-negative integer solutions.