The sum of n terms of a G.P. with first term a and common ratio r, when r = 1, is given by:

1. $S_n = \dfrac{a(1-r^n)}{1-r}$

2. $S_n = \dfrac{a(r^n-1)}{r-1}$

3. n²a

4. na

The sum of n terms of a G.P. with first term a and common ratio r, when r > 1, is :

1. $\dfrac{ar^n-1}{r-1}$

2. $\dfrac{1-ar^n}{1-r}$

3. $\dfrac{a(r^n-1)}{r-1}$

4. $\dfrac{a(1-r^n)}{1-r}$

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