Tìm x , biết: (a) x − 1/3 = 1/2 ; (b) ( 2 x + 3 ) ( x + 2 ) = ( x − 4 ) ( 2 x + 1 ) .

a) \[\frac{{x - 1}}{3} = \frac{1}{2}\]

\(2.\left( {x - 1} \right) = 3.1\)

\(2x - 2 = 3\)

\(x = \frac{5}{2}\)

Vậy \(x = \frac{5}{2}\).

b) \(\left( {2x + 3} \right)\left( {x + 2} \right) = \left( {x - 4} \right)\left( {2x + 1} \right)\)

\(2{x^2} + 4x + 3x + 6 = 2{x^2} + x - 8x - 4\)

\(14x = - 10\)

\(x = - \frac{5}{7}\)

Vậy \(x = - \frac{5}{7}\).