Question

chung to rang tong 1+3+3^2+...+3^99 chia het cho 40

Answer 1

= (1+ 3 + 3² + 3³) +...+ (3⁹⁶ + 3⁹⁷ + 3⁹⁸ + 3⁹⁹⁾

⁼ 40 + ...+ 3⁹⁶( 1 + 3 + 3² + 3³)

= 40 +...+3⁹⁶. 40

= 40( 1 +...+3⁹⁶) : hết cho 40

 

Answer 2

nguyễn thanh hải tick nha, chtt

Answer 3

1+3+3^2+...+3^99

= (1+ 3 + 3² + 3³) +...+ (3⁹⁶ + 3⁹⁷ + 3⁹⁸ + 3⁹⁹⁾

⁼ 40 + ...+ 3⁹⁶( 1 + 3 + 3² + 3³)

= 40 +...+3⁹⁶. 40

= 40( 1 +...+3⁹⁶) : hết cho 40