a/ \(\left(12x-5\right)\left(4x-1\right)+\left(3x-7\right)\left(1-16x\right)=81\)

<=> \(48x^2-12x-20x+5+3x-48x^2-7+112x=81\)

<=> \(83x-2=81\)

<=> \(83x=83\)

<=> \(x=1\)

b/ \(\left(2x-3\right)\left(2x+3\right)-\left(4x+1\right)x=1\)

<=> \(4x^2-9-4x^2-x=1\)

<=> \(-\left(9+x\right)=1\)

<=> \(9+x=-1\)

<=> \(x=-10\)

c/ \(3x^2-\left(x+2\right)\left(3x-1\right)=-7\)

<=> \(3x^2-\left(3x^2-x+6x-2\right)=-7\)

<=> \(3x^2-3x^2+x-6x+2=-7\)

<=> \(-5x+2=-7\)

<=> \(-5x=-9\)

<=> \(x=\frac{9}{5}\)

#)Giải :

Câu 1 :

5x(1 - 2x ) - 3x ( x+18) = 0 

<=> 5x - 10x^2 - 3x^2 - 54x = 0 

<=> -13x^2 - 49x = 0 

<=> x= 0 hoặc x = - 49/13

Vậy x có hai giá trị là 0 và - 49/13

#)Giải :

Câu 2 :

( 12x - 5 )( 4x - 1 ) + ( 3x - 7 )( 1 - 16x ) = 81

<=> 48x² - 32x + 5 - 48x + 115x - 7 = 81

<=> 83x - 2 = 81

<=> x = 1

Vậy x = 1

1)5x(1 - 2x ) - 3x ( x+18) = 0 
<=> 5x - 10x^2 - 3x^2 - 54x = 0 
<=> -13x^2 - 49x = 0 
<=> x= 0 hoặc x = -49/13

2) <=> 48x^2 - 12x - 20x + 5 + 3x - 48x^2 - 7 + 112x = 81 

<=> -32x + 115x = 81 + 2 
<=> 83x = 83 
<=> x = 1

\(\left(12x-5\right)\left(4x-1\right)\left(3x-7\right)\left(1-16x\right)=81\)

\(\Rightarrow\left(48x^2-12x-20x+5\right)\left(3x-7\right)\left(1-16x\right)=81\)

\(\Rightarrow\left(48x^2-32x+5\right)\left(3x-7\right)\left(1-16x\right)=81\)

\(\Rightarrow\left(144x^3-336x^2-96x^2+224x+15x-35\right)\left(1-16x\right)=81\)

\(\Rightarrow\left(144x^3-432x^2+239x-35\right)\left(1-16x\right)=81\)

\(\Rightarrow144x^3-2304x^4-432x^2+6912x^3+239x-3824x^2-35+560x=81\)

\(\Rightarrow-2304x^4+7056x^3-4256x^2+799x-116=0\)

\(\Rightarrow\left[{}\begin{matrix}x_1\approx2,3\\x_2\approx0,5\end{matrix}\right.\)

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

=> \(2x^2+3\left(x^2-1\right)=5x^2+5x\)

=> \(2x^2+3x^2-3-5x^2-5x=0\)

=> \(-3-5x=0\)

=> \(5x=-3\Rightarrow x=-\frac{3}{5}\)

\(x\left(2x-1\right)\left(x+5\right)-\left(2x^2+1\right)\left(x+\frac{9}{2}\right)=\frac{7}{2}\)

=> \(x\left[2x\left(x+5\right)-1\left(x+5\right)\right]-2x^2\left(x+\frac{9}{2}\right)-1\left(x+\frac{9}{2}\right)=\frac{7}{2}\)

=> \(x\left(2x^2+10x-x-5\right)-2x^3-9x^2-x-\frac{9}{2}=\frac{7}{2}\)

=> \(2x^3+10x^2-x^2-5x-2x^3-9x^2-x-\frac{9}{2}=\frac{7}{2}\)

=> \(\left(2x^3-2x^3\right)+\left(10x^2-x^2-9x^2\right)+\left(-5x-x\right)-\frac{9}{2}=\frac{7}{2}\)

=> \(-6x-\frac{9}{2}=\frac{7}{2}\)

=> \(-6x=8\Rightarrow x=-\frac{8}{6}=-\frac{4}{3}\)

\(\left(12x-5\right)\left(4x-1\right)+\left(3x-7\right)\left(1-16x\right)=81\)

=> 12x(4x - 1) - 5(4x - 1) + 3x(1 - 16x) - 7(1 - 16x) = 81

=> 48x² - 12x - 20x + 5 + 3x - 48x² - 7 + 112x = 81

=> -12x - 20x + 3x + 112x + 5 - 7 = 81

=> 83x + 5 - 7 = 81

=> 83x = 81 + 7 - 5

=> 83x = 83

=> x = 1

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

\(\Leftrightarrow2x^2+3x^2-3-5x^2-5x=0\)

\(\Leftrightarrow5x=-3\)

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

2) \(x\left(2x-1\right)\left(x+5\right)-\left(2x^2+1\right)\left(x+\frac{9}{2}\right)=\frac{7}{2}\)

\(\Leftrightarrow2x^3+9x^2-5x-2x^3-9x^2-x-\frac{9}{2}=\frac{7}{2}\)

\(\Leftrightarrow-6x=8\)

\(\Rightarrow x=-\frac{4}{3}\)

3) \(\left(12x-5\right)\left(4x-1\right)+\left(3x-7\right)\left(1-16x\right)=81\)

\(\Leftrightarrow48x^2-32x+5-48x^2+115x-7=81\)

\(\Leftrightarrow83x=83\)

\(\Rightarrow x=1\)

a) 2x² + 3( x - 1 )( x + 1 ) = 5x( x + 1 )

<=> 2x² + 3( x² - 1 ) = 5x² + 5x

<=> 2x² + 3x² - 5x² - 5x = 3

<=> -5x = 3

<=> x = -3/5

b) x( 2x - 1 )( x + 5 ) - ( 2x² + 1 )( x + 9/2 ) = 7/2

<=> x( 2x² + 9x - 5 ) - ( 2x³ + 9x² + x + 9/2 ) = 7/2

<=> 2x³ + 9x² - 5x - 2x³ - 9x² - x - 9/2 = 7/2

<=> -6x - 9/2 = 7/2

<=> -6x = 8

<=> x = -8/6 = -4/3

c) ( 12x - 5 )( 4x - 1 ) + ( 3x - 7 )( 1 - 16x ) = 81

<=> 48x² - 32x + 5 + 115x - 48x - 7 = 81

<=> 83x - 2 = 81

<=> 83x = 83

<=> x = 1

(12x - 5)(4x - 1) + (3x - 7)(1 - 16x) = 81

48x² - 32x + 5 - 48x + 115x - 7     = 81

83x - 2                                        = 81

83x                                             = 83

=> x                                           = 1

Sửa lại dòng 2 : 48x² - 32x + 5 - 48x² + 115x - 7 = 81

(12x-5).(4x-1)+(3x-7).(1-16x) = 81

  => 48x²-12x-20x+5+3x-48x²-7+112x = 81

  => 83x-2 = 81

  => 83x    = 81+2

  => 83x    = 83

  => x        = 83:83

 => x         = 1