Bài 1: Tìm x, biết     

a )24-(36+5)=x                              b)14-21=(13-x)-(15+8)                         

    24-41=x                                      (13-x)-23=-7 

    x=-17                                          13-x=(-7)+23

Vậy x=-17                                        13-x=16

                                                        x=13-16

                                                        x=-3                 Vậy x=-3

Bài 2:Tìm x, biết

a)17-x=-25+(-16+9)                           b)3x-21=-19-(-2x)                

   17-x=-25+(-7)                                   3x-21=-19+2x

    17-x=-32                                         3x-2x=-19+21

     x=17-(-32)                                       x=4

     x=49                                                    Vậy x=4

Vậy x=49

Bài 1:

a. 24 - (36+5) = x

=> 24 - 41 = x

=> -17 = x

=> x = -17

b. 14 - 21 = (13 - x) - (15 + 8)

=> -7 = 13 - x - 23

=> -7 - 13 + 23 = -x

=> 3 = -x

=> x = -3

Bài 2:

a. 17 - x = -25 + (-16 + 9)

=> 17 - x = -25 + (-7)

=> 17 - x = -32

=> 17 + 32 = x 

=> x = 49

b. 3x - 21 = -19 - (-2x)

=> 3x - 21 = -19 + 2x

=> 3x - 2x = -19 + 21

=> x = 2

Bài1

a)24-(36+5)=x\(\Rightarrow\)x=24-41=-17

b)14-21=(13-x)-(15+8)\(\Rightarrow\)(13-x)-(15+8)=-7\(\Rightarrow\)13-x=-7+23=16\(\Rightarrow\)x=13-16=-3

Bài2

a)17-x=-25+(-16+9)\(\Rightarrow\)17-x=-25+-7\(\Rightarrow\)17-x=-32\(\Rightarrow\)x=17-(-32)=17+32=49

b)3x-21=-19-(-2x)\(\Rightarrow\)3x-(-2x)=-19-21\(\Rightarrow\)3x+2x=-40\(\Rightarrow\)5x=-40\(\Rightarrow\)x=-8

ta co (2x-1)(3x+1)+(3x+4)(3-2x)=5

     (=)6x²-3x+2x-1+6x-6x²+12-8x=5

     (=)-4x+11=5

     (=)-4x=-6

     (=)x=3/2

(2x-1)(3x+1)+(3x-4)(3-2x)=5

<=> 6x²+2x-3x-1+9x-6x²-12+8x=5

<=> 16x-13=5

<=> 16x = 18

<=> x=9/8

a) \(\frac{45-\left(3x+9\right)}{13}=42\)

\(\Leftrightarrow45-\left(3x+9\right)=546\)

\(\Leftrightarrow3x+9=-501\)

\(\Leftrightarrow3x=-510\)

\(\Leftrightarrow x=-170\)

b) \(\left(x+1\right)+\left(2x+2\right)+...+\left(20x+20\right)=1050\)

\(\Leftrightarrow x+1+2x+2+...+20x+20=1050\)

\(\Leftrightarrow\left(x+1\right)+2\left(x+1\right)+....+20\left(x+1\right)=1050\)

\(\Leftrightarrow\left(x+1\right)\left(1+2+3+...+20\right)=1050\)

\(\Leftrightarrow\left(x+1\right)\left[\frac{\left(20+1\right).20}{2}\right]=1050\)

\(\Leftrightarrow\left(x+1\right).210=1050\)

\(\Leftrightarrow x+1=5\)

\(\Leftrightarrow x=4\)

B, => 2x+5=3x-8

2x-3x=-8-5

-x=-13

=>x=13

hoặc 2x+5=-3x+8

2x+3x=8-5

5x=3

x=\(\frac{3}{5}\)

\(\left|x+1\right|+\left|x-5\right|=7.\)

\(Th1:x+1< 0;x-5< 0\)

\(x< -1;x< 5\Rightarrow x< -1\)

\(\left|x+1\right|+\left|x-5\right|=7\)

\(-\left(x+1\right)-\left(x-5\right)=7\)

\(-x-1-x+5=7\)

\(-2x+4=7\)

\(-2x=3\)

\(x=-1,5\left(tm\right)\)

\(Th2:x+1>0;x-5>0\)

\(x>-1;x>5\Rightarrow x>5\)

\(\left|x+1\right|+\left|x-5\right|=7\)

\(x+1+x-5=7\)

\(2x-4=7\)

\(2x=11\)

\(x=5,5\)\(\left(tm\right)\)

\(Th3:x+1\le0;x-5>0\)

\(x\le-1;x>5\)(không xảy ra)

\(Th4:x+1>0;x-5\le0\)

\(x>-1;x\le5\Rightarrow-1< x\le5\)

\(\left|x+1\right|+\left|x-5\right|=7\)

\(-\left(x+1\right)+x-5=7\)

\(-x-1+x-5=7\)( không xảy ra) 

Vậy  x = -1,5 hoặc x = 5,5

\(\)

\(\left|2x+5\right|=3x-8.\)

\(Th1:\)

\(2x+5=-\left(3x-8\right)\)

\(2x+5=-3x+8\)

\(2x+3x=8-5\)

\(5x=3\)

\(x=\frac{3}{5}\)

\(Th2:\)

\(2x+5=3x-8\)

\(2x-3x=-8-5\)

\(-x=-13\)

\(x=13\)

Vậy x = 13 hoặc x = \(\frac{3}{5}\)

Ta có:

|2x-5|+1=3x

=> |2x-5|=3x-1

=> 2x-5=3x-1 ; 2x-5=1-3x

=> -5+1=3x-2x ; 2x+3x=1+5

=>x=-4 ; 5x =6

; x=\(\dfrac{5}{6}\)

Tìm x thuoc z:

1) \(26-\left|x+9\right|=-13\)

\(\Leftrightarrow\left|x+9\right|=26-\left(-13\right)\)

\(\Leftrightarrow\left|x+9\right|=39\)

\(\Leftrightarrow\left[{}\begin{matrix}x+9=39\\x+9=-39\end{matrix}\right.\)

\(\Leftrightarrow\left[{}\begin{matrix}x=39-9=30\\x=-39-9=-48\end{matrix}\right.\)

Vậy: \(x\in\left\{30;-48\right\}\)

2) \(\left|x+7\right|-13=25\)

\(\Leftrightarrow\left|x+7\right|=25+13=38\)

\(\Leftrightarrow x+7\in\left\{38;-38\right\}\)

\(\Leftrightarrow x\in\left\{31;-45\right\}\)

Vậy:.................

tim x biet

\(1)123-3.\left(x+4\right)=23\)

\(\Leftrightarrow3\left(x+4\right)=123-23\)

\(\Leftrightarrow3\left(x+4\right)=100\)

\(\Leftrightarrow x+4=\frac{100}{3}\)

\(\Leftrightarrow x=\frac{100}{3}-4=\frac{100-12}{3}=\frac{88}{3}\)

Vậy:................

2) Tương tự