Supaya 1+2+2²+2³+ ... +2n = 255 tentukan nilai n

jawab
1 + 2 + 2² + 2³ + ...+ 2ⁿ = 255
1  + 2 + 4 + 8 +...+ 2ⁿ = 255
2 + 4 + 8 + ...+ 2ⁿ = 255 - 1 = 254
a = 2
r = 2
Sn = 2 (rⁿ - 1) / (r - 1)
254 = 2 (2ⁿ - 1) / ( 2 - 1)
254 = 2 (2ⁿ - 1)
2ⁿ - 1 = 127
2ⁿ = 128 = 2⁷
n = 7