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A=2+2^2+2^3+2^4+2^5+2^6+2^7+2^8+2^9+2^10
=(2+2^2)+(2^3+2^4)+(2^5+2^6)+(2^7+2^8)+(2^9+2^10)
=2(1+2)+2^3(1+2)+2^5(1+2)+2^7(1+2)+2^9(1+2)
=(1+2)(2+2^3+2^5+2^7+2^9)
=3(2+2^3+2^5+2^7+2^9) chia hết cho 3
\(=2\left(1+2\right)+2^3\left(1+2\right)+2^5\left(1+2\right)+2^7\left(1+2\right)+2^9\left(1+2\right)\)
\(=3\left(2+2^3+2^5+2^7+2^9\right)⋮3\)
Ta có :
\(2+2^2+2^3+....+2^{10}\)
\(=2\left(1+2\right)+2^3\left(1+2\right)+....+2^9\left(1+2\right)\)
\(=2.3+2^3.3+....+2^9.3\)
=> Tổng chia hết cho 3
\(2+2^2+2^3+...+2^{10}\)
\(=\left(2+2^2\right)+\left(2^3+2^4\right)+...+\left(2^9+2^{10}\right)\)
\(=2\left(1+2\right)+2^3\left(1+2\right)+...+2^9\left(1+2\right)\)
\(=2.3+2^3.3+...+2^9.3\)
\(=\left(2+2^3+...+2^9\right).3⋮3\)
\(\Rightarrow2+2^2+2^3+...+2^{10}⋮3\)
Có nha bạn.
Có nha bạn.
Có nha bạn.
ban kia lam dung roi do
k tui nha
thanks
bạn kia làm đúng rồi
k tui nha
thank
A=2+2^2+2^3+2^4+2^5+2^6+2^7+2^8+2^9+2^10
A=(2+2^2)+2^2.(2+2^2)+2^4.(2+2^2)+2^6.(2+2^2)+2^8.(2+2^2)
A=6+2^2.6+2^4.6+2^6.6+2^8.6
A=(1+2^2+2^4+2^6+2^8).6
Vì 6 chia hết cho 3 nên A chia hết cho 3.
\(A=2+2^2+2^3+2^4+...+2^{10}\)
\(A=\left(2+2^2\right)+\left(2^3+2^4\right)+...+\left(2^9+2^{10}\right)\)
\(A=2.\left(1+2\right)+2^3.\left(1+2\right)+...+2^9.\left(1+2\right)\)
\(A=2.3+2^3.3+...+2^9.3\)
\(A=3.\left(2+2^3+...+2^9\right)\)
\(\Rightarrow A⋮3\)
A=(2+2^2)+(2^3+2^4)+(2^5+2^6)+(2^7+2^8)+(2^9+2^10)
A=2.(1+2)+2^3.(1+2)+2^5.(1+2)+2^7.(1+2)+2^9.(1+2)
A=3.(2+2^3+2^5+2^7+2^9) chia hết cho 3 vì thừa số 3 chia hết cho 3.