Question

tinh

D =1/ 2²  +1/ 2³ +1/2⁴ +..... +1/ 2¹⁰⁰

Answer 1

2D = 1/2 + 1/2² + 1/2³ + ... + 1/2⁹⁹

2D - D = (1/2 + 1/2² + 1/2³ + ... + 1/2⁹⁹) - (1/2² + 1/2³ + 1/2⁴ + ... + 1/2¹⁰⁰)

D = 1/2 - 1/2¹⁰⁰

Answer 2

2D = 1/2 + 1/2² + 1/2³ + ... + 1/2⁹⁹

2D - D = (1/2 + 1/2² + 1/2³ + ... + 1/2⁹⁹) - (1/2² + 1/2³ + 1/2⁴ + ... + 1/2¹⁰⁰)

D = 1/2 - 1/2¹⁰⁰