\[\frac{4b^{2} - 6b + 1}{ab^{2}} - \frac{b - 5^{\backslash b}}{\text{ab}} =\]
\[= \frac{4b^{2} - 6b + 1 - b(b - 5)}{ab^{2}} =\]
\[= \frac{4b^{2} - 6b + 1 - b^{2} + 5b}{ab^{2}} =\]
\[= \frac{3b^{2} - b + 1}{ab²}\]