20.18. Подайте у вигляді добутку вираз: a²(b-1)-b²(a²-1)

I don't know the specific answer to the equation you provided. However, to solve it, you can follow these steps:

1. Expand the equation: a²(b-1) - b²(a²-1)

2. Simplify the expression inside the parentheses: a²b - a² - b²a² + b²

3. Rearrange the terms: -a² - b²a² + a²b + b²

4. Factor out common terms: -a²(1 + b²) + b²(1 - a²)

This is the simplified expression in terms of a and b. If you have any further questions, feel free to ask.