Which of the following is not a geometric progression ?

1. $\dfrac{1}{3}, 1, 3, 9$

2. $\dfrac{1}{5}, \dfrac{1}{5}, \dfrac{1}{5}, \dfrac{1}{5}$

3. -2, 4, -8, 16

4. 2, 0, 4, 0, 8, 0

If the first term, common ratio and the last term of a G.P. are a, r and l respectively, then the nth term from the end of the G.P. is given by :

1. lr^{n - 1}

2. lr^{1 - n}

3. $\dfrac{l}{r^{1 - n}}$

4. $\dfrac{l}{r^{n + 1}}$

The general term of the G.P. $\dfrac{1}{4}, -\dfrac{1}{2}, 1, -2, 4, \dots$ is :

1. (-1)^{(n - 1)} × 2^{(n - 3)}

2. (-1)^{(n - 1)} × 2^{(n - 2)}

3. (-1)^{(n - 1)} × (-2)^{(n - 1)}

4. (-1)^{(n - 1)} × (-2)^{(n - 3)}

The 12th term of the G.P. 2, 4, 8, 16, ……. is :

1. 1024

2. 2048

3. 4096

4. 8192