[tex] \\(\frac{2}{3}-\frac{1}{2})^2-(\frac{3}{4}-\frac{2}{5})^2=\\ (\frac{4}{6}-\frac{3}{6})^2-(\frac{15}{20}-\frac{8}{20})^2=\\ (\frac{1}{6})^2-(\frac{7}{20})^2=\\ \frac{1}{36}-\frac{49}{400}=\\ \frac{100}{3600}-\frac{441}{3600}=\\ -\frac{341}{3600}\\ [/tex]
