[latex]1) \frac{2b-5}{ b^{2}-5b }+ \frac{1}{5-b} [/latex]

[latex] \frac{2b-5}{b^2-5b} + \frac{1}{5-b}= \frac{2b-5}{b(b-5)} - \frac{1}{b-5}= \frac{2b-5-b}{b(b-5)} =\frac{b-5}{b(b-5)} = \frac{1}{b} [/latex]