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

1. 0

2. 1

3. 1.2

4. 1.44

If 4 × 2^{x + 3} = 8^{x + 1}, then 2^x =

1. 1

2. 2

3. 4

4. 8

If 2^{x + 3} + 2^{x + 1} = 320, then x =

1. 2

2. 3

3. 4

4. 5