Объяснение:

1. (a - 3)² - a(a - 6) = a² - 6a + 9 - a² + 6a = 9

2. (x + 5)² - (x - 5)² = (x + 5 - (x - 5))(x + 5 + x - 5) = 10 * 2x = 20x

3. (z - 2)² + (z - 5)(z + 7) = z² - 4z + 4 + z² - 5z + 7z - 35 =

= 2z² - 2z - 31

4. 1 - (2x - 1)² = (1 - (2x - 1))(1 + 2x - 1) = (1 - 2x + 1)(1 + 2x - 1) =

= (2 - 2x) * 2x = 4x - 4x² = -4x² + 4x