Bài 1:

\(a.\left|x\right|+\left|6\right|=\left|-27\right|\\ \Leftrightarrow\left|x\right|+6=27\\ \Leftrightarrow\left|x\right|=27-6=21\\ \Leftrightarrow\left\{{}\begin{matrix}x=-21\\x=21\end{matrix}\right.\)

a. $\left|x\right|$ + $\left|+6\right|$ = $\left|-27\right|$

x + 6 = 27

x = 27 - 6

x = 21

Vậy x = 21

b. $\left|-5\right|$ . $\left|x\right|$ = $\left|-20\right|$

5 . x = 20

x = 20 : 5

x 4

Vậy x = 4

c. = và x > 0

|x| = 17

Vì |x| = 17

nên x = -17 hoặc 17

mà x > 0 => x = 17

Vậy x = 17 hoặc x = -17

d. $\left|x\right|$ = $\left|23\right|$ và x < 0

|x| = 23

Vì |x| = 23

nên x = 23 hoặc -23

mà x < 0 => x = -23

e. 12 $\le$$\left|x\right|$ < 15

Vì 12 < 15

nên x = {12; 13; 14}

Vậy x € {12; 13; 14}

f. |x| > 3

Vì |x| > 3

nên x = -2; -1; 0; 1; 2;

Vậy x € {-2; -1; 1; 2}

a. A=

$\{$

$x\in Z|-3<x\le 7\}$

A = {-2; -1; 0; 1; 2; 3; 4; 5; 6; 7}

b. B=$\left\{x\in Z|3\le \left|x\right|<7\right\}$

B = {3; 4; 5; 6}

c. C=$\left\{x\in Z|\left|x\right|>5\right\}$

C = {6; 7; 8; 9; ...}

Câu a:

(-15 + |\(x\)|) + (25 - |-\(x\)|)

= -15 + |\(x\)| + 25 - |\(x\)|

= (25- 15) + (|\(x\)| - |\(x\)|)

= 10 + 0

= 10

b; \(x-34\) - [(15 + \(x\)) -(23 - \(x\))]

\(x-34\) - 15 - \(x\) + 23 - \(x\)

(\(x-x-x\)) - (34 + 15 - 23)

= (0 - \(x\)) - (49 - 23)

= -\(x\) - 26

a) \(\left|2x-1\right|=5\)

\(\Rightarrow\left[\begin{matrix}2x-1=5\\2x-1=-5\end{matrix}\right.\)

\(\Rightarrow\left[\begin{matrix}2x=6\\2x=-4\end{matrix}\right.\)

\(\Rightarrow\left[\begin{matrix}x=3\\x=-2\end{matrix}\right.\)

Vậy \(x\left[\begin{matrix}=3\\=-2\end{matrix}\right.\)

b) \(\left(5^x-1\right)3-2=70\)

\(\Rightarrow5^x.3-3=72\)

\(\Rightarrow5^x.3=75\)

\(\Rightarrow5^x=5^2\)

\(\Rightarrow x=2\)

Vậy \(x=2.\)

c) \(\left(x-1\frac{1}{2}\right)^2+\frac{3}{4}=\frac{1}{4}\)

\(\Rightarrow\left(x-1\frac{1}{2}\right)^2=\frac{-1}{2}\)

............. Làm tiếp nhé!

d) \(\left(\frac{1}{1.2.3}+\frac{1}{2.3.4}+...+\frac{1}{8.9.10}\right)x=\frac{23}{45}\)

\(\left(\frac{1}{1.2.3}+\frac{1}{2.3.4}+...+\frac{1}{8.9.10}\right)x=\frac{23}{45}\)

\(\Rightarrow\frac{1}{2}\left(\frac{1}{1.2}-\frac{1}{2.3}+\frac{1}{2.3}-\frac{1}{3.4}+...+\frac{1}{8.9}-\frac{1}{9.10}\right)x=\frac{23}{45}\)

\(\Rightarrow\frac{1}{2}\left(\frac{1}{1.2}-\frac{1}{9.10}\right)x=\frac{23}{45}\)

\(\Rightarrow\frac{1}{2}.\frac{22}{45}x=\frac{23}{45}\)

\(\Rightarrow\frac{11}{45}x=\frac{23}{45}\)

\(\Rightarrow x=\frac{23}{45}:\frac{11}{45}\)

\(\Rightarrow x=\frac{23}{11}\)

câu 1:23+3x=5mu3=125-23=102:3=34.the la xong.minh lam tat

23 + 3x = 5⁶ : 5³

=> 23 + 3x = 5³

=> 23 + 3x = 125

=> 3x = 102

=> x = 34

(x - 6)² = 9

=> x - 6 = 3 hoặc x - 6 = - 3

=> x = 9 hoặc x = 3

vậy_

x - 2 = -6 + 17                                              \(|\)x - 4 \(|\)= \(|\)- 81\(|\)

x - 2 = 9                                                          x - 4 = 81     

x       = 9 + 2                                                    x      = 81 + 4

x       = 11                                                        x       = 85

a) 25 : x = x

25 = x^2

x^2 = ( +-5 )^2

b) 3358 : 23 = 2x - 6

146 = 2x - 6

2x = 152

x = 76

c) ( 2x + 1 )^3 = 27 = 3^3

=> 2x + 1 = 3

=> 2x = 2

=> x = 1

d) ( x - 2 )^3 = ( x - 2 )^2

( x - 2 )^2 . ( x - 2 ) - ( x -2 )^2 = 0

( x - 2 )^2 . [ ( x - 2 ) - 1 ] = 0

+) x - 2 = 0

=> x = 2

+) x - 2 - 1 = 0

x - 3 = 0

x = 3

\(25\div x=x\Rightarrow x.x=25\Rightarrow x^2=25\Rightarrow\orbr{\begin{cases}x=5\\x=-5\end{cases}}\)

\(3358\div23=2x-6\)

\(\Rightarrow2x-6=146\)

\(\Rightarrow2x=152\)

\(\Rightarrow x=\frac{152}{2}=76\)

\(\left(2x+1\right)^3=27\)

Mà \(3^3=27\)

Nên \(\left(2x+1\right)^3=3^3\)

\(\Rightarrow2x+1=3\Rightarrow2x=2\Rightarrow x=1\)

\(\left(x-2\right)^3=\left(x-2\right)^2\)

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

\(\Rightarrow\left(x-2\right)^2.\left(x-2-1\right)=0\)

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

\(\Rightarrow\orbr{\begin{cases}x-2=0\\x-3=0\end{cases}\Leftrightarrow\orbr{\begin{cases}x=2\\x=3\end{cases}}}\)

Vậy......................

240=2⁴.3.5

210=2.3.5.7

180=2².3².5

_ƯCLN (240;210;180)=2.3.5=30

mỗi phần thưởng có số bút bi là

240:30=8 cây

Khi đó mỗi phần thưởng có số bút chì là

210:30=7 cây

Khi đó mỗi phần thưởng có số tập giấy là

180:30=6 tập

Đáp số..........

Làm hết bài dễ chết quá

Bài 5 nè 

I x+3 I \(\ge\)0\(\Rightarrow\)A \(\ge\)4  

Vậy min A = 4 khi x = -3 

câu b t tự

a) \(\frac{2x}{5}-1=\frac{1}{4}.\left(-5\right)=-\frac{5}{4}\)

\(\frac{2}{5}.x=\left(-\frac{5}{4}\right)+1=-\frac{1}{4}\)

\(x=-\frac{1}{4}:\frac{2}{5}=-\frac{5}{8}\)

b) \(x=\left(-5,75\right):\frac{14}{23}=-\frac{23}{4}:\frac{14}{23}=-\frac{529}{56}\)

a) \(\Rightarrow\left(2x:5-1\right)=\frac{1}{4}.\left(-5\right)=-\frac{5}{4}\)

\(\Rightarrow2x:5=-\frac{5}{4}+1=-\frac{1}{4}\)

\(\Rightarrow2x=-\frac{1}{4}.5=-\frac{5}{4}\)

\(\Rightarrow x=-\frac{5}{4}:2=-\frac{5}{8}\)

b) \(\Rightarrow x=-5.75:\frac{14}{23}=-\frac{529}{56}\)

a) (x - 45) . 27 = 0

x - 45 = 0 : 27

x - 45 = 0

x = 0 + 45

x = 45

b) 23 . (42 - x) = 23

42 - x = 23 : 23

42 - x = 1

- x = 1 + (-42)

-x = -41

x = 41

a) ( x - 45 ) . 27 = 0

Suy ra: x - 45 = 0

x = 0 + 45

x = 45

b) 23 . ( 42 - x) = 23

42 - x = 23 : 23

42 - x = 1

x = 42 - 1

x = 41

\(f\)) \(32^{-x}.16^x=1024\)

\(\left(2\right)^{-5x}.2^{4x}=2^{10}\)

\(\Leftrightarrow2^{4x-5x}=2^{10}\)

\(\Leftrightarrow2^{-x}=2^{10}\)

\(\Leftrightarrow-x=10\)

\(\Leftrightarrow x=-10\)

\(g\)) \(3^{x-1}.5+3^{x-1}=162\)

\(3^{x-1}.\left(5+1\right)=162\)

\(3^{x-1}.6=162\)

\(3^{x-1}=162:6\)

\(3^{x-1}=27\)

\(\Leftrightarrow3^{x-1}=3^3\)

\(\Leftrightarrow x-1=3\)

\(\Leftrightarrow x=4\)

\(h\)) \(\left(2x-1\right)^6=\left(2x-1\right)^8\)

\(\Leftrightarrow\left(2x-1\right)^6-\left(2x-1\right)^8=0\)

\(\Leftrightarrow\left(2x-1\right)^6-\left(2x-1\right)^6.\left(2x-1\right)^2=0\)

\(\Leftrightarrow\left(2x-1\right)^6.\left[1-\left(2x-1\right)^2\right]=0\)

\(\Leftrightarrow\orbr{\begin{cases}\left(2x-1\right)^6=0\\1-\left(2x-1\right)^2=0\end{cases}}\Leftrightarrow\orbr{\begin{cases}2x-1=0\\\left(2x-1\right)^2=1\end{cases}}\)\(\Leftrightarrow\orbr{\begin{cases}2x=1\\\left(2x-1\right)^2=\left(1,-1\right)^2\end{cases}}\)

\(\Leftrightarrow\hept{\begin{cases}x=\frac{1}{2}\\2x-1=-1\\2x-1=1\end{cases}}\)\(\Leftrightarrow\hept{\begin{cases}x=\frac{1}{2}\\2x=0\\2x=2\end{cases}}\)\(\Leftrightarrow\hept{\begin{cases}x=\frac{1}{2}\\x=0\\x=1\end{cases}}\)

\(i\)) \(5^x+5^{x+2}=650\)

\(5^x.\left(1+5^2\right)=650\)

\(5^x.26=650\)

\(5^x=650:26\)

\(5^x=25\)

\(\Leftrightarrow5^x=5^2\)

\(\Leftrightarrow x=2\)