Question

Answer 1

1: \(A=2\left(1+2+2^2+2^3\right)+2^5\left(1+2+2^2+2^3\right)+2^9+2^{10}\)

\(=30\left(2+2^5\right)+1536\)

=> A ko chia hết cho 5

2: \(B=2\left(1+2\right)+2^3\left(1+2\right)+...+2^{99}\left(1+2\right)\)

\(=3\left(2+2^3+...+2^{99}\right)⋮3\)

3: \(C=5\left(1+5\right)+5^3\left(1+5\right)+5^5\left(1+5\right)\)

=6(5+5^3+5^5) chia hết cho 6

4: D=3(1+3)+3^3(1+3)+3^5(1+3)

=4(1+3^3+3^5) chia hết cho 4

5: E=4(1+4)+4^3(1+4)+4^5(1+4)

=5*(4+4^3+4^5) chia hết cho 5

Answer 2

KO CHÉP ĐỀ BÀI NHÉ

1.Ta có :

2A = 2.(2 + 2² + 2³ + 2⁴ + 2⁵ + 2⁶ + 2⁷ + 2⁸ + 2⁹ + 2¹⁰) 

2A = 2² + 2³ + 2⁴ + 2⁵ + 2⁶ + 2⁷ + 2⁸ + 2⁹ + 2¹⁰ + 2¹¹

2A - A = (2² + 2³ + 2⁴ + 2⁵ + 2⁶ + 2⁷ + 2⁸ + 2⁹ + 2¹⁰ + 2¹¹) - (2 + 2² + 2³ + 2⁴ + 2⁵ + 2⁶ + 2⁷ + 2⁸ + 2⁹ + 2¹⁰)

        A = 2² + 2³ + 2⁴ + 2⁵ + 2⁶ + 2⁷ + 2⁸ + 2⁹ + 2¹⁰ + 2¹¹ -  2 -  2²  -  2³  - 2⁴ -  2⁵ - 2⁶  - 2⁷ - 2⁸ - 2⁹ - 2¹⁰

        A = 2¹¹ - 2

Vì 2 ko chia hết cho 5 nên A ko chia hết cho 5