Tìm giá trị của x , biết: (a) 2 x − 3/4 = x + 1/7 ; (b) ( x^4 − 5 x^3 − 3 x^2 ) : x^2 − ( x + 1 ) ( x − 2 ) = 3 .

a) \(\frac{{2x - 3}}{4} = \frac{{x + 1}}{7}\)

\(7.\left( {2x - 3} \right) = 4.\left( {x + 1} \right)\)

\(14x - 21 = 4x + 4\)

\(10x = 25\)

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

Vậy \(x = \frac{5}{2}\).

b) \(\left( {{x^4} - 5{x^3} - 3{x^2}} \right):{x^2} - \left( {x + 1} \right)\left( {x - 2} \right) = 3\)

\({x^2} - 5x - 3 - \left( {{x^2} - 2x + x - 2} \right) = 3\)

\({x^2} - 5x - 3 - {x^2} + 2x - x + 2 = 3\)

\( - 4x - 1 = 3\)

\( - 4x = 4\)

\(x = - 1\)

Vậy \(x = - 1\).