Đáp án:
$\begin{array}{l}
a){x^2} - 16 - 4xy + 4{y^2}\\
= {x^2} - 4xy + 4{y^2} - 16\\
= {\left( {x - 2y} \right)^2} - {4^2}\\
= \left( {x - 2y + 2} \right)\left( {x - 2y - 2} \right)\\
b){x^5} - {x^4} + {x^3} - {x^2}\\
= {x^4}\left( {x - 1} \right) + {x^2}\left( {x - 1} \right)\\
= \left( {x - 1} \right)\left( {{x^4} + {x^2}} \right)\\
= \left( {x - 1} \right)\left( {{x^2} + 1} \right).{x^2}\\
c)4{x^2} + 4x - 3\\
= 4{x^2} + 4x + 1 - 4\\
= {\left( {2x + 1} \right)^2} - {2^2}\\
= \left( {2x + 1 - 2} \right)\left( {2x + 1 + 2} \right)\\
= \left( {2x - 1} \right)\left( {2x + 3} \right)
\end{array}$
