=-9+{-54:[256+7].4}

=-9+{-54: 263 .4}

=-9+ -216/263

=-2583/263

\(\overline{ab}+\overline{ba}\\=a\cdot10+b+b\cdot10+a\\=10a+b+10b+a\\=(10a+a)+(10b+b)\\=11a+11b\\=11\cdot(a+b)\)

Vì \(11\cdot(a+b)\vdots11\)

nên \(\overline{ab}+\overline{ba}\vdots11\).

chịu

a)

\(x+4⋮x\)

\(\Rightarrow\left(x+4\right)-x⋮x\)

\(\Rightarrow4⋮x\)

\(\Rightarrow x\in\left\{1;-1;2;-2;4;-4\right\}\)

b) \(\left(75-x\right)\left(x+32\right)\left(x-58\right)=0\)

\(\Rightarrow75-x=0;x+32=0;x-58=0\)

\(\Rightarrow x=75;x=-32;x=58\)

Ngu

B=1+5+5^2+....+5^20

5B=5+5^2+5^3+...+5^21

5B-B=(5+5^2+5^3+...+5^21)-(1+5+5^2+...+5^20)

4B=5^21-1

=>4B+1=5^21

Vì 4B+1=5^x

=>5^x=5^21

=>x=21

Vậy.....

tick cho mình nhé

Chứng minh: A=2+2^2+2^3+...+2^100 chia hết cho 6

A=(2+2^2)+(2^3+2^4)+...+(2^99+2^100)

=6+2^2.(2+2^2)+...+2^98.(2+2^2)

=6+2^2.6+...+2^98.6

=6.(1+2^2+...+2^98) chia hết cho 6.

 Vậy A chia hết cho 6

 nhớ tick cho mig nha

a)diện tích lối đi:9x2=18(m'2)

b)diện tích khu vườn là:9x4-18=18(m'2)

số tiền cần phải trả là:18x50000=900000(đồng)

    39 x31+ 39x68 +39

=39x(31+68+1)

=39x100

=3900

39x3x(31+68)

=117 x (31+68)

117 x 99

= 11583

\(B=2^2+2^3+2^4+...+2^{121}\\=(2^2+2^3)+(2^4+2^5)+(2^6+2^7)+...+(2^{120}+2^{121})\\=2^2\cdot(1+2)+2^4\cdot(1+2)+2^6\cdot(1+2)+...+2^{120}\cdot(1+2)\\=2^2\cdot3+2^4\cdot3+2^6\cdot3+...+2^{120}\cdot3\\=3\cdot(2^2+2^4+2^6+...+2^{120})\)

Vì \(3\cdot(2^2+2^4+2^6+...+2^{120})\vdots3\)

nên \(B\vdots3\)