Solve for x :

9^{x + 2} = 720 + 9^x

(20⁰ - 18⁰) x 7⁰ is equal to:

1. 0

2. 1

3. 14

4. none of these

If $\dfrac{a}{b} = \dfrac{2}{3} ÷ \Big(-\dfrac{2}{3}\Big)^0; \text{then} \Big(\dfrac{a}{b}\Big)^{-2}$ is equal to:

1. $\dfrac{4}{9}$

2. $-\dfrac{4}{9}$

3. $\dfrac{9}{4}$

4. $-\dfrac{9}{4}$

If 5^{2x + 3} = 1, the value of x is:

1. $\dfrac{3}{2}$

2. $-\dfrac{3}{2}$

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

4. $-\dfrac{2}{3}$