Which of the following is equivalent to the sum Sn=a1+a1r+a1r2+⋯+a1rn−1S_n = a_1 + a_1r + a_1r^2 + \dots + a_1r^{n-1}Sn=a1+a1r+a1r2+⋯+a1rn−1?
Sn=a11−rS_n = \frac{a_1}{1-r}Sn=1−ra1
Sn=a1⋅rnS_n = a_1 \cdot r^nSn=a1⋅rn
Sn=a1(1−r)1−rnS_n = \frac{a_1(1-r)}{1-r^n}Sn=1−rna1(1−r)
Sn=a1(1−rn)1−rS_n = \frac{a_1(1-r^n)}{1-r}Sn=1−ra1(1−rn)