Tìm giá trị của x , biết: (a) x − 3 , 28 = − 6 , 38 . (b) 11/9 − x = 5/3 .

a) \(x - 3,28 = - 6,38\)

\(x = - 6,38 + 3,28\)

\(x = - 3,1\)

Vậy \(x = - 3,1.\)

b) \(\frac{{11}}{9} - x = \frac{5}{3}\)

\(x = \frac{{11}}{9} - \frac{5}{3}\)

\(x = - \frac{4}{9}.\)

Vậy \(x = - \frac{4}{9}.\)

c) \(\frac{4}{5}.x + \frac{1}{5} = \frac{4}{{15}}\)

\(\frac{4}{5}x = \frac{4}{{15}} - \frac{1}{5}\)

\[\frac{4}{5}x = \frac{1}{{15}}\]

\[x = \frac{1}{{15}}:\frac{4}{5}\]

\[x = \frac{1}{{12}}\]

Vậy \(x = \frac{1}{{12}}.\)

d) \({\left( {x - \frac{1}{4}} \right)^2} + \frac{3}{8} = \frac{{31}}{{16}}\)

\({\left( {x - \frac{1}{4}} \right)^2} = \frac{{31}}{{16}} - \frac{3}{8}\)

\({\left( {x - \frac{1}{4}} \right)^2} = \frac{{25}}{{16}}\)

\({\left( {x - \frac{1}{4}} \right)^2} = {\left( {\frac{5}{4}} \right)^2}\)

\(x - \frac{1}{4} = \frac{5}{4}\) hoặc \(x - \frac{1}{4} = - \frac{5}{4}\)

\(x = \frac{5}{4} + \frac{1}{4}\) \(x = - \frac{5}{4} + \frac{1}{4}\)

\(x = \frac{3}{2}\) \(x = - 1\)

Vậy \(x = \frac{3}{2};x = - 1.\)