Question

A=5^29+5^28+5^27+...+5^3+5^2+5^2+5+1

giải hộ mình nha

Answer 1

ta có: A = 5²⁹ + 5²⁸ + 5²⁷ + ...+ 5³ + 5² + 5 + 1

=> 5A = 5³⁰ + 5²⁹ + 5²⁸ + ...+ 5⁴ + 5³ + 5² + 5

=> 5A - A = 5³⁰ - 1

\(A=\frac{5^{30}-1}{4}\)

Answer 2

\(A=5^{29}+5^{28}+5^{27}+...+5^3+5^2+5+1\) 

=> \(5A=5^{30}+5^{29}+5^{28}+....+5^4+5^3+5^2+5\) 

=> \(5A-A=5^{30}-1\) 

=> \(4A=5^{30}-1\) => \(A=\frac{5^{30}-1}{4}\)