(12x - 5)(4x + 3) + (3x - 5)(1 - 16x) = 81
⇔ 48x2 + 36x - 20x - 15 + 3x - 48x2 - 5 + 80x - 81 = 0
⇔ 99x - 101 = 0
⇔ x = \(\dfrac{101}{99}\)
\(\left(12x-5\right)\left(4x+3\right)+\left(3x-5\right)\left(1-16x\right)=81\)
\(\Leftrightarrow48x^2+36x-20x-15+3x-48x^2-5+80x=81\)
\(\Leftrightarrow99x=101\)
hay \(x=\dfrac{101}{99}\)