Tìm x, biết:a) 0,65.x = 0,65.0,1;b) - x - 3/2 = - 5/4

a) \(0,65.x = 0,65.\,0,1\)

\(x = \frac{{0,65.\,0,1}}{{0,65}}\)

\(x = 0,1\)

Vậy \(x = 0,1\).

b) \( - x - \frac{3}{2} = \frac{{ - 5}}{4}\)

\( - x = - \frac{5}{4} + \frac{3}{2}\)

\( - x = \frac{1}{4}\)

\(x = - \frac{1}{4}\)

Vậy \(x = - \frac{1}{4}\).

c) \[\left( {\frac{2}{3} - 2x} \right)\left( {x + \frac{4}{5}} \right) = 0\]

Suy ra \[\frac{2}{3} - 2x = 0\] hoặc \[x + \frac{4}{5} = 0\]

Trường hợp 1:

\[\frac{2}{3} - 2x = 0\]

\(2x = \frac{2}{3}\)

\(x = \frac{1}{3}\)

Vậy \[x \in \left\{ {\frac{1}{3};\frac{{ - 4}}{5}} \right\}\].

Trường hợp 2:

\[x + \frac{4}{5} = 0\]

\[x = \frac{{ - 4}}{5}\]