\(\begin{array}{l}
a)\, = xy\left( {2x - y + 5} \right)\\
b)\, = x\left( {x - y} \right) + 10\left( {x - y} \right) = \left( {x - y} \right)\left( {x + 10} \right)\\
c)\, = x\left( {{x^2} - 2x + 1 - {y^2}} \right)\\
= x\left( {{{\left( {x - 1} \right)}^2} - {y^2}} \right) = x\left( {x - 1 + y} \right)\left( {x - 1 - y} \right)
\end{array}\)