To factor $ x^{3}-x^{2}+25x-25 $ we can use factoring by grouping:
Group $ \color{blue}{ x^{3} }$ with $ \color{blue}{ -x^{2} }$ and $ \color{red}{ 25x }$ with $ \color{red}{ -25 }$ then factor each group.
$$ \begin{aligned} x^{3}-x^{2}+25x-25 = ( \color{blue}{ x^{3}-x^{2} } ) + ( \color{red}{ 25x-25 }) &= \\ &= \color{blue}{ x^{2}( x-1 )} + \color{red}{ 25( x-1 ) } = \\ &= (x^{2}+25)(x-1) \end{aligned} $$