\[\boxed{\text{858.\ }\text{еуроки}\text{-}\text{ответы}\text{\ }\text{на}\text{\ }\text{пятёрку}}\]
\[\textbf{а)}\ \frac{x^{2} - 10x + 25}{35 - 7x} =\]
\[= \frac{(x - 5)^{2}}{7 \cdot (5 - x)} = \frac{(x - 5)^{2}}{- 7 \cdot (x - 5)} =\]
\[= \frac{x - 5}{- 7} = \frac{5 - x}{7}\]
\[\textbf{б)}\ \frac{4x^{2} - 12x + 9}{(3 - 2x)^{2}} = \frac{(2x - 3)^{2}}{(3 - 2x)^{2}} =\]
\[= \frac{(2x - 3)²}{(2x - 3)²} = 1\]