Đáp án:
$\begin{array}{l}
a)3{x^2} + 8x + 4\\
= 3{x^2} + 6x + 2x + 4\\
= \left( {x + 2} \right)\left( {3x + 2} \right)\\
b)4{x^2} - 4x - 3\\
= 4{x^2} - 4x + 1 - 4\\
= {\left( {2x - 1} \right)^2} - {2^3}\\
= \left( {2x - 1 - 2} \right)\left( {2x - 1 + 2} \right)\\
= \left( {2x - 3} \right)\left( {2x + 1} \right)\\
c)9{x^2} + 12x - 5\\
= 9{x^2} + 2.3x.2 + 4 - 9\\
= {\left( {3x + 2} \right)^2} - {3^2}\\
= \left( {3x + 2 - 3} \right)\left( {3x + 2 + 3} \right)\\
= \left( {3x - 1} \right)\left( {3x + 5} \right)\\
d)6{x^2} - 11x + 3\\
= 6{x^2} - 9x - 2x + 3\\
= \left( {2x - 3} \right)\left( {3x - 1} \right)\\
e)2{x^2} + 3x - 27\\
= 2{x^2} + 9x - 6x - 27\\
= \left( {2x + 9} \right)\left( {x - 3} \right)\\
f){x^2} - 10x + 24\\
= {x^2} - 4x - 6x + 24\\
= \left( {x - 4} \right)\left( {x - 6} \right)\\
g)2{x^2} - 5xy + 2{y^2}\\
= 2{x^2} - xy - 4xy + 2{y^2}\\
= \left( {2x - y} \right)\left( {x - 2y} \right)
\end{array}$
