If $x^2 + \dfrac{1}{x^2} = 2$, the value of $x^2 - \dfrac{1}{x^2}$ is :

1. 0

2. 2

3. $\pm 2$

4. 8

If x + 3y + 2z = 0, the value of x³ + 27y³ + 8z³ is :

1. 9xyz

2. 6xyz

3. 18xyz

4. xyz

Find the cube of 5a + 3b.

Find the cube of 2a + $\dfrac{1}{2a}$, a ≠ 0;