a, (abc -cba)

= 100a+10b+c -(100c+10b+a)

=100a + 10b +c -100c -10b- a

=99a -99c

=99. (a-c) 

=9.11(a-c) chia hết cho 11

hok tốt !

Bài 2 hình như sai đề bn nha, 2a+3b+c mới đúng

\(\frac{10}{5}\)

a) 3x - 2 = 0    =>   3x = 2    => x = 2/3

b) 2x - 1 = 0     =>  2x = 1      =>  x = 1/2

c) 5 ( 4+2x) = 8+5x

<=> 20 + 10x = 8 + 5x

<=> 10x - 5x = 8 - 20

<=>  5x  =  -12

x = -12/5

d) \(\frac{1}{2}+\frac{3}{4}x=6-\frac{4}{5}x\)

\(\frac{3}{4}x+\frac{4}{5}x=6-\frac{1}{2}\)

\(\frac{31}{20}x=\frac{11}{2}\)

\(x=\frac{11}{2}:\frac{31}{20}=\frac{110}{31}\)

e) 3 + 2x = 4 - 8x

<=> 2x + 8x = 4 - 3

10 x = 1

x = 1/10

f \(5+\frac{1}{2}\left(x+5\right)=3\)

\(\frac{1}{2}\left(x+5\right)=3-5=-2\)

\(x+5=-2:\frac{1}{2}=-4\)

\(x=-4-5=1\)

Vậy ......

a, 3x - 2 = 0

=> 3x = 2

=> x = 2/3

vậy_

2⁸*5⁷=2.2.2.2.2.2.2.2.5.5.5.5.5.5.5=(2.5).(2.5).(2.5).(2.5).(2.5).(2.5).(2.5).2=10.10.10.10.10.10.10.2=10000000.2=20000000

\(2^8.5^7=2.2^8.5^8=2.10^8=200000000\)

a) \(\left(2x-15\right)^3=\left(2x-15\right)^5\)

\(\Rightarrow\left(2x-15\right)^3-\left(2x-15\right)^5=0\)

\(\Rightarrow\left(2x-15\right)^3\left[1-\left(2x-15\right)^2\right]=0\)

\(\Rightarrow\orbr{\begin{cases}\left(2x-15\right)^3=0\\1-\left(2x-15\right)^2=0\end{cases}}\Rightarrow\orbr{\begin{cases}\left(2x-15\right)^3=0\\\left(2x-15\right)^2=1\end{cases}}\)

TH 1 : \(\left(2x-15\right)^3=0\Rightarrow2x-15=0\Rightarrow2x=15\Rightarrow x=\frac{15}{2}\)

TH 2 : \(\left(2x-15\right)^2=1\Rightarrow\orbr{\begin{cases}2x-15=1\\2x-15=-1\end{cases}}\Rightarrow\orbr{\begin{cases}2x=16\\2x=14\end{cases}}\Rightarrow\orbr{\begin{cases}x=8\\x=7\end{cases}}\)

Vậy  \(x\in\left\{\frac{15}{2};8;7\right\}\)

b) \(x^{10}=x\)

\(\Rightarrow x^{10}-x=0\)

\(\Rightarrow x\left(x^9-1\right)=0\)

\(\Rightarrow\orbr{\begin{cases}x=0\\x^9-1=0\end{cases}}\Rightarrow\orbr{\begin{cases}x=0\\x^9=1\end{cases}}\Rightarrow\orbr{\begin{cases}x=0\\x=1\end{cases}}\)

Vậy x = 0 hoặc x = 1

c) \(x^{10}=1^0\)

\(\Rightarrow x^{10}=1\)

\(\Rightarrow\orbr{\begin{cases}x^{10}=1^{10}\\x^{10}=\left(-1\right)^{10}\end{cases}}\Rightarrow\orbr{\begin{cases}x=1\\x=-1\end{cases}}\)

Vậy x = 1 hoặc x = -1

_Chúc bạn học tốt_

Mơn pn

Vì \(9\le\left|x-3\right|\le11\) nên \(\left|x-3\right|=9,10,11\)

\(\Rightarrow x-3=\pm9;\pm10;\pm11\)

\(\Rightarrow x=12;-6;13;-7;14;-8\)

Vậy \(x=-8;-7;-6;12;13;14\)

\(x-3\in\left\{9;10;11\right\}\)

\(\Rightarrow x\in\left\{6;7;8\right\}\)

\(2n+1⋮16-3n\Rightarrow3.\left(2n+1\right)⋮16-3n\Leftrightarrow6n+3⋮16-3n\\ \)

Mà \(2.\left(16-3n\right)⋮16-3n\Leftrightarrow32-6n⋮16-3n\)

\(\Rightarrow6n+3+\left(32-6n\right)⋮16-3n\Leftrightarrow35⋮16-3n\)

Mà n thuộc N => 16-3n thuộc Z => 16-3n thuộc Ư{35}

\(\Rightarrow16-3n\in\left\{\pm1;\pm5;\pm7;\pm35\right\}\Rightarrow n\in\left\{5;7;3;17\right\}\)(vì n thuộc N)

\(\hept{\begin{cases}2n+1⋮16-3n\\16-3n⋮16-3n\end{cases}}\Rightarrow\hept{\begin{cases}3\left(2n+1\right)⋮16-3n\\2\left(16-3n\right)⋮16-3n\end{cases}}\)     <=>  \(\hept{\begin{cases}6n+3⋮16-3n\\32-6n⋮16-3n\end{cases}}\)  

  =>  6n+3 +(32 - 6n) \(⋮\)16- 3n  = 36 \(⋮\) 16 -3n 

     16 -3n\(\in\left\{1;2;3;4;9;13;18;6;36\right\}\)

  Vì n thuộc N => 16-3n thuộc N =>    3n\(\in\left\{15;14;13;12;7;3;10\right\}\)

                          n      \(\in\left\{5;4;1\right\}\)