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

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

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

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

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

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

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

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

a: =>2x^2-2x+2x-2-2x^2-x-4x-2=0

=>-5x-4=0

=>x=-4/5

b: =>6x^2-9x+2x-3-6x^2-12x=16

=>-19x=19

=>x=-1

c: =>48x^2-12x-20x+5+3x-48x^2-7+112x=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 

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

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

83x = 81 - 5 + 7

83x = 83

x = 83/83

x = 1

Chúc bn hok tốt nha

\(a,x\left(-3x+5\right)+3x\left(x+1\right)-40=0\)

\(\left(x.-3x\right)+\left(5x\right)+3x\left(x+1\right)-40=0\)

\(-3x^2+5x+\left(3x.x\right)+\left(3x.1\right)-40=0\)

\(-3x^2+5x+3x^2+3x-40=0\)

\(\left(-3x^2+3x^2\right)+5x+3x-40=0\)

\(8x-40=0\)

\(8x=0+40=40\)

\(x=40:8=5\)

a) \(x\left(5-3x\right)+3x\left(x+1\right)-40=0\)

\(\Rightarrow5x-3x^2+3x^2+3x-40=0\)

\(\Rightarrow8x-40=0\)

\(\Rightarrow8x=40\)

\(\Rightarrow x=5\)

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

\(\Rightarrow48x^2-12x-20x+5+3x-48x^2-7+112x=81\)

\(\Rightarrow83x=83\)

\(\Rightarrow x=1\)

có làm thì mới có ăn nhé bạn

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

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

=> 83x = 83

=> x = 1

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

\(\text{⇔}48x^2-32x+5-48x^2-7+115x=81\)

\(\text{⇔}83x-2=81\)

\(\text{⇔}83x=83\)

\(\text{⇔}x=1\)

Vậy: x=1

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

\(\Leftrightarrow48x^2-12x-20x+5+3x-48x^2-7+112x=81\)

\(\Leftrightarrow83x=83\)

hay x=1