Question

Tìm x, biết:

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

giải chi tiết luôn nha

Answer 1

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

( 12x.4x ) + ( 12x.1) + ( -5.4x) + ( -5).(-1) + 3x.1 + 3x. (-16x) + (-7).1 + ( -7 ).(-16x) = 81

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

\(\left(-12x-20x\right)\)\(+\left(5-7\right)\)\(+\left(3x+112x\right)\)\(=81\)

\(-32x-2+115x^2\)\(=81\)

\(\left(-32x^2+115x^2\right)-2\)\(=81\)

\(83x-2\)\(=81\)

\(83x=81+2\)

\(83x=83\)

\(\Rightarrow x=1\)

Answer 2

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

<=> 48x²-32x+5 +3x-48x²-7+112x=81

<=> 83x= 81 +2

<=> 83x=83

<=> x=1

Answer 3

(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 = 1