Đáp án:
16) \(27{x^3} + \dfrac{1}{8}{y^3}\)
Giải thích các bước giải:
\(\begin{array}{l}
12)4{x^2} + 12xy + 9{y^2}\\
= {\left( {2x} \right)^2} + 2.2x.3y + {\left( {3y} \right)^2}\\
= {\left( {2x + 3y} \right)^2}\\
13){x^3} + 3.{x^2}.2 + 3.4.x + {2^3}\\
= {\left( {x + 2} \right)^3}\\
14){\left( {5x} \right)^2} - 2.5x.4y + {\left( {4y} \right)^2}\\
= {\left( {5x - 4y} \right)^2}\\
15)\left( {2x - 3y} \right)\left( {4{x^2} + 2x.3y + 9{y^2}} \right)\\
= 8{x^3} - 27{y^3}\\
16)\left( {3x + \dfrac{1}{2}y} \right)\left( {9{x^2} - \dfrac{3}{2}xy + \dfrac{1}{4}{y^2}} \right)\\
= {\left( {3x} \right)^3} + {\left( {\dfrac{1}{2}y} \right)^3}\\
= 27{x^3} + \dfrac{1}{8}{y^3}
\end{array}\)
