a) ( 2x - 25 ) : 3 = 27

     ( 2x - 25 )     = 81

       2x               = 81 + 25

       2x               = 106

         x               = 53

b) ( x - 3 ) ( 8 - x ) = 0

\(\Rightarrow\orbr{\begin{cases}x-3=0\\8-x=0\end{cases}}\)\(\Rightarrow\orbr{\begin{cases}x=3\\x=8\end{cases}}\)

d) 516 - ( 246 + 3x ) = 26 

                246 + 3x   = 490

                           3x  = 244

                             x  = 

a)(2x - 25) : 3 = 27

=> 2x - 25 = 27 . 3

=> 2x - 25 = 81

=> 2x = 81 + 25 = 106

=> x = 106 : 2 = 53

b)(x - 3).(8 - x) = 0

=> x - 3 = 0 hoặc 8 - x = 0

=> x = 3 hoặc x = 8

c) 889 - 5x - 2x = 375

=>889 - 7x = 375

=>7x = 889 - 375

=>7x = 514 

=>x = 514/7

d) 516 - ( 246 + 3x ) = 26

=> 246 + 3x = 516 - 26

=> 246 + 3x = 490

=> 3x = 490 - 246

=> 3x = 244

=> x = 244/3

e) x + 1 + 2 + 3 + ... + 50 = 1500

=>x + (1 + 2 + 3 + ... + 50) = 1500

=>x + 50.(50+1):2 = 1500

=>x + 1275 = 1500

=>x = 1500 - 1275

=>x = 225

Tìm số tự nhiên x thỏa mãn  : 

a , ( 2x - 25 ) : 3 = 27 

2x - 25 = 27 × 3 

2x - 25 = 81 

2x = 81 + 25 

2x = 106 

x = 106 : 2 

x = 53 

Vậy x = 53 

b, ( x - 3 ) . ( 8 - x ) = 0 

<=> x - 3 = 0 hoặc 8 - x = 0

<=> x = 0 + 3 hoặc x = 8 - 0 

<=> x = 3 hoặc x = 8

Vậy x € { 3 ; 8 } 

a) ( x - 1 )² - ( x - 1 )( x + 1 ) = 0

<=> x² - 2x + 1 - ( x² - 1 ) = 0

<=> x² - 2x + 1 - x² + 1 = 0

<=> 2 - 2x = 0

<=> 2x = 2 

<=> x = 1

b) ( 2x - 1 )² - ( 2x + 1 )² = 0

<=> [ ( 2x - 1 ) - ( 2x + 1 ) ][ ( 2x - 1 ) + ( 2x + 1 ) ] = 0

<=> ( 2x - 1 - 2x - 1 )( 2x - 1 + 2x + 1 ) = 0

<=> -2.4x = 0

<=> -8x = 0

<=> x = 0

c) 25( x + 3 )² + ( 1 - 5x )( 1 + 5x ) = 8

<=> 5²( x + 3 )² + 1² - 25x² = 8

<=> [ 5( x + 3 ) ]² + 1 - 25x² = 8

<=> ( 5x + 15 )² + 1 - 25x² = 8

<=> 25x² + 150x + 225 + 1 - 25x² = 8

<=> 150x + 226 = 8

<=> 150x = -218

<=> x = -218/150 = -109/75

d) 9( x + 1 )² - ( 3x - 2 )( 3x + 2 ) = 10

<=> 3²( x + 1 )² - ( 9x² - 4 ) = 10

<=> [ 3( x + 1 ) ]² - 9x² + 4 = 10

<=> ( 3x + 3 )² - 9x² + 4 = 10

<=> 9x² + 18x + 9 - 9x² + 4 = 10

<=> 18x + 13 = 10

<=> 18x = -3

<=> x = -3/18 = -1/6

a) (x - 1)² - (x - 1)(x + 1) = 0

=> (x - 1)² - (x² - 1²) = 0

=> x² - 2.x.1 + 1² - x² + 1 = 0

=> x² - 2x + 1 - x² + 1 = 0

=> -2x + 1 + 1 = 0

=> -2x + 2 = 0

=> -2x = -2 => x = 1

b) (2x - 1)² - (2x + 1)² = 0

=> (2x - 1 - 2x + 1)(2x - 1 + 2x + 1) = 0

=> 0 = 0(đúng)

c) 25(x + 3)² + (1 - 5x)(1 + 5x) = 8

=> 25(x² + 2.x.3 + 3²) + (1² - (5x)²) = 8

=> 25x² + 150x + 225 + 1 - 25x² = 8

=> 150x +225 + 1 = 8

=> 150x = -218

=> x = -109/75

d) 9(x + 1)² - (3x - 2)(3x + 2) = 10

=> 9(x² + 2x + 1) - [(3x)² - 2²  ] = 10

=> 9x² + 18x + 9 - (9x² - 4) = 10

=> 9x² + 18x + 9 - 9x² + 4 = 10

=> 18x + 9 + 4 = 10

=> 18x = -3

=> x = -1/6

a) \(\left(x-1\right)^2-\left(x-1\right)\left(x+1\right)=0\)

\(\Leftrightarrow\left(x-1\right)\left(x-1-x-1\right)=0\)

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

\(\Leftrightarrow x-1=0\)

\(\Rightarrow x=1\)

b) \(\left(2x-1\right)^2-\left(2x+1\right)^2=0\)

\(\Leftrightarrow-2.4x=0\)

\(\Rightarrow x=0\)

c) \(25\left(x+3\right)^2+\left(1-5x\right)\left(1+5x\right)=8\)

\(\Leftrightarrow25x^2+150x+225+1-25x^2-8=0\)

\(\Leftrightarrow150x=-218\)

\(\Rightarrow x=-\frac{109}{75}\)

d) \(9\left(x+1\right)^2-\left(3x-2\right)\left(3x+2\right)=10\)

\(\Leftrightarrow9x^2+18x+9-9x^2+4=10\)

\(\Leftrightarrow18x=-3\)

\(\Rightarrow x=-\frac{1}{6}\)

1/ => 2x + 1 = 0 => 2x = -1 => x = -1/2

hoặc 3x - 9 = 0 => 3x = 9 => x = 3

Vậy x = { -1/2 ; 3 }

2/ => x² = 0 => x = 0 

hoặc 2/3 - 5x = 0 => 5x = 2/3 => x = 2/15

Vậy x = 2/15 ; x = 0

3/ 2x - 7 = 7 - 2x

=> 2x + 2x = 7 + 7 

=> 4x = 14

=> x = 7/2

Vậy x = 7/2

6(1-x)+4(2-x)<=3(1-3x)

=>6-6x+8-4x<=3-9x

=>-10x+14<=-9x+3

=>-x<=-11

=>x>=11

(1-2x)/4-2<-5x/8

=>2-4x-16<-5x

=>-4x-14<-5x

=>x<14

Số tự nhiên x thỏa mãn cả hai BPT khi và chỉ khi 11<=x<14

=>\(x\in\left\{11;12;13\right\}\)

\(a,\left(-2+x\right).\left(3x-6\right)=0\)

\(\Leftrightarrow\orbr{\begin{cases}-2+x=0\\3x-6=0\end{cases}\Leftrightarrow\orbr{\begin{cases}x=2\\x=2\end{cases}\Leftrightarrow}x=2}\)

Vậy ................

\(b,\left(3x+9\right)\left(2x+6\right)=0\)

\(\Leftrightarrow\orbr{\begin{cases}3x+9=0\\2x+6=0\end{cases}}\Leftrightarrow\orbr{\begin{cases}x=-3\\x=-3\end{cases}\Leftrightarrow x=-3}\)

Vậy ......................

a)\(\(\left(-2+x\right)\left(3x-6\right)=0\)\)

\(\(\Leftrightarrow\orbr{\begin{cases}-2+x=0\\3x-6=0\end{cases}\Leftrightarrow\orbr{\begin{cases}x=2\\x=2\end{cases}\Rightarrow}x=2}\)\)

b) cmtt

_Minh ngụy_

a,         ( -2 + x ) . ( 3x - 6 ) = 0 

\(\orbr{\begin{cases}-2+x=0\\3x-6=0\end{cases}\Leftrightarrow\orbr{\begin{cases}x=2\\3x=6\end{cases}\Leftrightarrow}\orbr{\begin{cases}x=2\\x=2\end{cases}}}\)

b,  ( 3x + 9 ) . ( 2x + 6 ) = 0 

\(\orbr{\begin{cases}3x+9=0\\2x+6=0\end{cases}\Leftrightarrow\orbr{\begin{cases}3x=-9\\2x=-6\end{cases}\Leftrightarrow}\orbr{\begin{cases}x=-3\\x=-3\end{cases}}}\)