Đáp án:
$\begin{array}{l}
a){x^4} + {x^3} + 4{x^2} + 2x + 4\\
= {x^4} + {x^3} + 2{x^2} + 2{x^2} + 2x + 4\\
= {x^2}\left( {{x^2} + x + 2} \right) + 2\left( {{x^2} + x + 2} \right)\\
= \left( {{x^2} + x + 2} \right)\left( {{x^2} + 2} \right)\\
b){\left( {2ab - 2cd} \right)^2} - {\left( {{a^2} + {b^2} - {c^2} - {d^2}} \right)^2}\\
= \left( {2ab - 2cd - {a^2} - {b^2} + {c^2} + {d^2}} \right).\\
\left( {2ab - 2cd + {a^2} + {b^2} - {c^2} - {d^2}} \right)\\
= \left[ {{{\left( {c - d} \right)}^2} - {{\left( {a - b} \right)}^2}} \right].\left[ {{{\left( {a + b} \right)}^2} - {{\left( {c + d} \right)}^2}} \right]\\
= \left( {c - d - a + b} \right)\left( {c - d + a - b} \right).\left( {a + b + c + d} \right)\left( {a + b - c - d} \right)
\end{array}$
Bạn xem lại đề bài câu c
