Question

S=1+5+5²+5³...5¹⁰

tìm S

 

Answer 1

S = 1 + 5 + 5 ² + 5 ³ + ... + 5 ¹⁰

5S = 5 + 5 ² + 5 ³ + 5 ⁴ + ... + 5 ¹¹

5S - S = ( 5 + 5 ² + 5 ³ + 5 ⁴ + ... + 5 ¹¹ )

            - ( 1 + 5 + 5 ² + 5 ³ + ... + 5 ¹⁰ )

  4S    = 5 ¹¹ - 1

=> \(S=\frac{5^{11}-1}{4}\)

Answer 2

S = 1 + 5 + 5 ² + 5 ³ + ... + 5 ¹⁰

5S = 5 + 5 ² + 5 ³ + 5 ⁴ + ... + 5 ¹¹

5S - S = ( 5 + 5 ² + 5 ³ + 5 ⁴ + ... + 5 ¹¹ )

            - ( 1 + 5 + 5 ² + 5 ³ + ... + 5 ¹⁰ )

  4S    = 5 ¹¹ - 1

    S    = \(\frac{5^{11}-1}{4}\)

Answer 3

thank bai nay minh tuong ko ai bit chu