\[5x^{3} - x^{2} - 5x + 1 =\]
\[= x^{2} \cdot (5x - 1) - (5x - 1) =\]
\[= (5x - 1)\left( x^{2} - 1 \right),\]
\[при\ x = 0,2:\]
\[(5 \cdot 0,2 - 1)(0,04 - 1) = 0.\ \]