[tex]1) \frac{(5a-6)(5a+6)}{(5a-2)(2a-1)} *\frac{5a-2}{5a+6}=\frac{5a-6}{2a-1};\\ 2) \frac{5a-6}{2a-1}+\frac{9a-8}{1-2a}=\frac{9a-8-5a+6}{2a-1}=\frac{4a-2}{2a-1}=\frac{2(2a-1)}{2a-1}=2[/tex]

Що й треба було довести.