Tìm x, biết: a) 2/3 x - 2/5 = 1/2 x - 1/3 b) 1/3 x + 2/5 (x + 1) = 0

* Hướng dẫn giải

$\begin{array}{l}a)\frac{2}{3}x-\frac{2}{5}=\frac{1}{2}x-\frac{1}{3}\\ \left(\frac{2}{3}-\frac{1}{2}\right)x=-\frac{1}{3}+\frac{2}{5}\\ \frac{1}{6}x=\frac{1}{15}\\ x=\frac{2}{5}\end{array}$

$\begin{array}{l}b)\frac{1}{3}x+\frac{2}{5}\left(x+1\right)=0\\ \left(\frac{1}{3}+\frac{2}{5}\right)x=-\frac{2}{5}\\ \frac{11}{15}x=-\frac{2}{5}\\ x=-\frac{6}{11}\end{array}$