Tìm x , biết: a) 1/5 x + 2/3 = 3/5 ; b) − 8/x + 2 =( x + 2)/ − 2 .

a) \(\frac{1}{5}x + \frac{2}{3} = \frac{3}{5}\)

    \(\frac{1}{5}x = \frac{3}{5} - \frac{2}{3}\)

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

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

      \(x = \frac{{ - 1}}{3}\)

 Vậy \(x = \frac{{ - 1}}{3}\).

b) \(\frac{{ - 8}}{{x + 2}} = \frac{{x + 2}}{{ - 2}}\)

 \(\left( {x + 2} \right).\left( {x + 2} \right) = \left( { - 8} \right).\left( { - 2} \right)\)

\({\left( {x + 2} \right)^2} = 16\)

Trường hợp 1:

\(x + 2 = 4\)

\(x = 4 - 2\)

\(x = 2\)

Trường hợp 2:

\(x + 2 = - 4\)

\(x = - 4 - 2\)

\(x = - 6\)

Vậy \(x \in \left\{ {2; - 6} \right\}\).