Question

tìm x ;          <12x-5><4x-1>+<3x-7><1-16x>=81

Answer 1

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

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

<=>-32x+115x=81+2 

<=>83x=83  

<=>x=1

Answer 2

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

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

<=>-32x+115x=81+2 

<=>83x=83  

<=>x=1

Answer 3

VT = (12x – 5)(4x – 1) + (3x – 7)(1 – 16x)

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

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

     = 48x2 – 12x – 20x + 5 + 3x – 48x2 – 7 + 112x

     = (48x2 – 48x2) + (– 12x – 20x + 3x + 112x) + (5 – 7)

     = 83x – 2

Vậy ta có:

83x – 2 = 81

       83x = 81 + 2

       83x = 83

           x = 83 : 83

           x = 1