Question

rút gọn biểu thức sau : A = 1+1/2²+1/2³+...+1/2²⁰¹⁵

Answer 1

A = 1 + 1/2²+1/2³+...+1/2²⁰¹⁵

(1-1/2) A = (1-1/2) (1+1/2²+1/2³+...+1/2²⁰¹⁵) = 1 - 1/2²⁰¹⁶

A = 2 *( 1 -1/2²⁰¹⁶) = 2 -1/2²⁰¹⁵

Answer 2

A = 1 + 1/2²+1/2³+...+1/2²⁰¹⁵

(1-1/2) A = (1-1/2) (1+1/2²+1/2³+...+1/2²⁰¹⁵) = 1 - 1/2²⁰¹⁶

A = 2 *( 1 -1/2²⁰¹⁶) = 2 -1/2²⁰¹⁵