$\Big[\Big(\sqrt[3]{a^4}\Big)^{\dfrac{-3}{2}}\Big]^{\dfrac{-1}{2}}$ =

1. a

2. a²

3. $\dfrac{1}{a}$

4. $\dfrac{1}{a^2}$

$\dfrac{\sqrt{5 \times 3^{-3}} \times \sqrt[6]{5 \times 3^6}}{\sqrt[6]{5} \times \sqrt{3}}$ =

1. $\sqrt{\dfrac{3}{5}}$

2. $\sqrt{\dfrac{5}{3}}$

3. $\dfrac{3}{5}$

4. $\dfrac{\sqrt{5}}{3}$

If 3^x = 3^-x, then (1.2)^x =

1. 0

2. 1

3. 1.2

4. 1.44

If $9 \times 81^x = \dfrac{1}{27^{(x - 3)}}$, then x =

1. 0

2. -1

3. 1

4. 3