Đáp án:
\(\begin{array}{l}
a){x^2}\left( {\dfrac{2}{5}x - 2y + 5} \right)\\
c)\dfrac{5}{4}\left( {y + 2} \right)\left( {3y - {x^2}} \right)\\
b)3xy\left( {2x - 5y + 7xy} \right)\\
d)6\left( {x - y} \right)\left( {2x + 3y} \right)
\end{array}\)
Giải thích các bước giải:
\(\begin{array}{l}
a)\dfrac{2}{5}{x^3} - 2{x^2}y + 5{x^2} = {x^2}\left( {\dfrac{2}{5}x - 2y + 5} \right)\\
c)\dfrac{{15}}{4}y\left( {y + 2} \right) - \dfrac{5}{4}{x^2}\left( {y + 2} \right)\\
= \left( {y + 2} \right)\left( {\dfrac{{15}}{4}y - \dfrac{5}{4}{x^2}} \right)\\
= \dfrac{5}{4}\left( {y + 2} \right)\left( {3y - {x^2}} \right)\\
b)6{x^2}y - 15x{y^2} + 21{x^2}{y^2}\\
= 3xy\left( {2x - 5y + 7xy} \right)\\
d)12x\left( {x - y} \right) - 18y\left( {y - x} \right)\\
= 12x\left( {x - y} \right) + 18y\left( {x - y} \right)\\
= \left( {x - y} \right)\left( {12x + 18y} \right)\\
= 6\left( {x - y} \right)\left( {2x + 3y} \right)
\end{array}\)
