\(\left(12x-5\right)\left(4x-1\right)+\left(3x-7\right)\left(1-16x\right)=81\)
\(48x^2-32x+5-48x+115x-7=81\)
\(83x-2=81\)
\(83x=83\)
=> x = 1
(12x-5)(4x-1)+(3x-7)(1-16x)=81
\((48x^2-12x-20x+5)+(3x-48x^2-7+112x^2)=81\)
\(48x^2-12x-20x+5+3x-48x^2-7+112x^2=81\)
\(48x^2-48x^2+112x^2-12x+20x+3x+5-7=81\)
\(112x^2+11x-12=81\)
\(112x^2+11x=93\)
Đến đây r tịt
Ta có: \(\left(12x-5\right)\left(4x-1\right)+\left(3x-7\right)\left(1-16x\right)=81\)
\(48x^2-12x-20x+5+3x-48x^2-7+112x=81\)
\(83x-2=81\)
\(83x=83\)
\(\Rightarrow x=83:83=1\)
