x² - (a + b)x + ab is the expansion of :

1. (x - b)(x - a)

2. (x - b)(x + a)

3. (x + b)(x - a)

4. (x + a)(x + b)

If a + b - c = 4 and a² + b² + c² = 14, the value of ab - bc - ca is :

1. 2

2. 1

3. 0.5

4. -0.5

Expand (x + 8)(x + 10)

Expand (x + 8)(x - 10)