Question

Hitunglah n jika diketahui 1+2+4+8+...+2ⁿ-¹ =127

Answer 1

 1 + 2 +4 +8+...+2^(n-1) = 127
a= 1
r = 2
Sn = 127
.
sn = a( r^n -1)/(r-1)
Sn = 1(2^n -1)/(2-1)
Sn = 2^n - 1
.
2^n - 1= 127
2^n = 128 = 2^7
n= 7