Question

Cho A= 2+2^2+2^3+2^4+2^5+2^6+2^7+2^8+2^9. Không tính, hãy chứng tỏ A:7

Giúp mik vs

Mik cần cho ngày mai

Answer 1

\(a=2+2^2+2^3+2^4+2^5+2^6+2^7+2^8+2^9\)

\(a=\left(2+2^2+2^3\right)+\left(2^4+2^5+2^6\right)+\left(2^7+2^8+2^9\right)\)

\(a=2\left(1+2+2^2\right)+2^4\left(1+2+2^2\right)+2^7\left(1+2+2^2\right)\)

\(a=2.7+2^4.7+2^7.7=7\left(2+2^4+2^7\right)⋮7\left(đpcm\right)\)

Answer 2

A=(2+2^2+2^3)+(2^4+2^5+2^6)+(2^7+2^8+2^9)

A=2(1+2+2^2)+2^4(1+2+2^2)+2^7(1+2+2^2)

A=2.7+2^4.7+2^7.7\(⋮\)7

Vậy A\(⋮\)7

Answer 3

Cho A= 2+2^2+2^3+2^4+2^5+2^6+2^7+2^8+2^9. Không tính, hãy chứng tỏ A:7

A=(2+2^2+2^3)+(2^4+2^5+2^6)+(2^7+2^8+2^9)

A=2(1+2+2^2)+2^4(1+2+2^2)+2^7(1+2+2^2)

A=2.7+2^4.7+2^7.7 \(⋮\) 7

Vậy A \(⋮\) 7