[tex]\frac{2a}{b^{2}-4a^{2}}+\frac{1}{2a-b} = \frac{2a}{b^{2}-4a^{2}}-\frac{1}{b-2a}=\frac{2a-1(b+2a)}{b^{2}-4a^{2}} = \frac{2a-b-2a}{b^{2}-4a^{2}}= \frac{-b}{b^{2}-4a^{2}}=-\frac{b}{b^{2}-4a^{2}}[/tex]