Tìm x, biết: a,(3x – 1) (2x +7) – (x+1) (6x-5) = 16 b, (10x +9) x – (5x-1) (2x+3) = 8

$a.(3x – 1)(2x +7) – (x+1)(6x-5) = 16 \\⇔6x^2+19x-7-6x^2-x+5=16 \\⇔18x-2=16 \\⇔18x=18 \\⇔x=1 \\ Vậy\ x=1 \\b.(10x+9)x-(5x-1)(2x+3)=8 \\⇔10x^2+9x-10x^2-13x+3=8 \\⇔-4x+3=8 \\⇔-4x=5 \\⇔x=\dfrac{-5}{4} \\Vậy\ x=\dfrac{-5}{4}$