Kinda been stuck on this one, someone pls let me know

Question

asked Jun 11, 2021 3.9k views

2 Answers

DanceIgel · Answer 1 · 2021-06-13T01:42:34+0000

Answer:

255

Explanation:

∑ᵢ₌₁⁸ 2ⁱ⁻¹

Using brute force method:

S = 2⁰ + 2¹ + 2² + 2³ + 2⁴ + 2⁵ + 2⁶ + 2⁷

S = 1 + 2 + 4 + 8 + 16 + 32 + 64 + 128

S = 255

Using formula:

S = a₁ (1 − rⁿ) / (1 − r)

S = 1 (1 − 2⁸) / (1 − 2)

S = 255