If $p + \dfrac{1}{p} = x\text{ and }p - \dfrac{1}{p} = y$, then the relation between x and y is :

1. x² = y²

2. x² + y² = 4

3. x² - y² = 4

4. xy = 2

If $a = \dfrac{1}{a - 7}$, then $a - \dfrac{1}{a}$ =

1. 0

2. 1

3. 7

4. $\dfrac{1}{7}$

If $\Big(x + \dfrac{1}{x}\Big)^2 = 3$, then $x^3 + \dfrac{1}{x^3}$ =

1. 9

2. 3

3. 2

4. 0

The value of ab if 3a + 5b = 15 and 9a² + 25b² = 75 is :

1. 4

2. 5

3. 6

4. 8