Hãy nhập câu hỏi của bạn vào đây, nếu là tài khoản VIP, bạn sẽ được ưu tiên trả lời.
a)A=(2+22)+(23+24)+...(29+210)
A=2(2+1)+23(1+2)+....+29(2+1)
A=3(2+23+25+27+29)
Vay A chia het cho 3(khi chia 3 duoc 2+23+25+27+29du 0)
b)A=(2+22+23+24+25)+(26+27+28+29+210)
A=2(1+2+22+23+24)+26(1+2+22+23+24)
A=31(2+26) luon chia het cho 31 :))
\(A=1+3+3^2+.....+3^{11}\)
\(A=\left(1+3+3^2\right)+....+\left(3^9+3^{10}+3^{11}\right)\)
\(A=\left(3^0.1+3^0.3+3^0.3^2\right)+....+\left(3^9.1+3^9.3+3^9.3^2\right)\)
\(A=1.\left(1+3+3^2\right)+....+3^9\left(1+3+3^2\right)\)
\(A=1.13+....+3^9.13\)
\(A=13.\left(1+....+3^9\right)⋮13\left(đpcm\right)\)
bai 1 ta co ab-ba=10a+b-10b-b=(10a-a)-(10b-b)=9a-9b=9.(a-b). vi 9.(a-b) chia het cho 9 suy ra (ab-ba) chia het cho 9 voi a>b (dpcm)
\(A=3\left(1+3+3^2\right)+3^4\left(1+3+3^2\right)\)\(=\left(1+3+3^2\right)\left(3+3^4\right)\)\(=13\left(3+3^4\right)\)
Và hiển nhiên tích này chia hết cho 13.
Vậy \(A=3+3^2+3^3+...+3^6⋮13\)
a/ (3n)100=(3n)4.25=(81n)25 chia hết cho 81.
b/ tao biết mà tự làm đi dễ lắm
c/ dựa vào dấu hiệu chia hết cho 9
b) \(\left(3+3^2+3^3\right)+\left(3^4+3^5+3^6\right)+.........+\left(3^{28}+3^{29}+3^{30}\right)\)
\(3\left(13\right)+3^4\left(13\right)+..........+3^{28}\left(13\right)\)
\(13\left(3+3^4+.........+3^{28}\right)⋮13\)
c/ \(10^{2015}+17\)
\(10^{2015}+17=1000.........00000000+17\)
\(=10000......0000017\)
\(1+0+0+0+0+....0+1+7=9⋮9\)
2a/ 2x - 3 = 16 => 2x - 3 = 24 => x - 3 = 4 => x = 7
b/ {x2 - [82 - (52 - 8.3)3 - 7.9]3 - 4.12}3 = 1
=> x2 - [82 - (52 - 8.3)3 - 7.9]3 - 4.12 = 1
=> x2 - [64 - (25 - 24)3 - 63]3 - 48 = 1
=> x2 - (64 - 1 - 63)3 = 1 + 48
=> x2 - 0 = 49
=> x2 = 49
=> x = 7
\(A=\left(1+3+3^2\right)+3^3\left(1+3+3^2\right)+...+3^{96}\left(1+3+3^2\right)\)
\(=13+3^3.13+...+3^{96}.13\)
\(=13\left(1+3^3+...+3^{96}\right)⋮13\)
\(A=\left(1+3+3^2\right)+\left(3^3+3^4+3^5\right)+...+\left(3^{96}+3^{97}+3^{98}\right)\\ A=\left(1+3+3^2\right)+3^3\left(1+3+3^2\right)+...+3^{96}\left(1+3+3^2\right)\\ A=\left(1+3+3^2\right)\left(1+3^3+...+3^{96}\right)\\ A=13\left(1+3^3+...+3^{96}\right)⋮13\)