(a + b) (a - b) + (b - c) (b + c) + (c + a) (c - a) is equal to:

1. 2a² + 2b² + 2c²

2. a² + b² + c² - 2ab - 2bc - 2ca

3. 0

4. none of these

(3x - 4y)² - (3x + 4y)² is equal to:

1. 18x² + 32y²

2. 18x² - 32y²

3. -48xy

4. 48xy

The value of (0.8)² - 0.32 + (0.2)² is equal to:

1. 1

2. 3.6

3. 0.36

4. 0.036

The value of (a - b - c)(a - b + c) is:

1. a² + b² + c² + 2ab

2. a² + b² - c² - 2ab

3. a² + b² + c² - 2ab

4. a² + b² - c² + 2ab