Tính. 2x(3y + 1)

* Hướng dẫn giải

a) \(\begin{array}{l}
{\rm{2x(3y  +  1) =  2x}}{\rm{.3y  +  2x}}{\rm{.1}}\\
{\rm{ =  6xy  + 2x}}
\end{array}\)

b)

\(\begin{array}{l}
{\rm{2xy(2}}{{\rm{x}}^{\rm{2}}} - {{\rm{x}}^{\rm{3}}}{{\rm{y}}^{\rm{2}}}{\rm{) =  2xy}}{\rm{.2}}{{\rm{x}}^2} - {\rm{2xy}}{\rm{.}}{{\rm{x}}^{\rm{3}}}{{\rm{y}}^{\rm{2}}}\\
 = {\rm{4}}{{\rm{x}}^{\rm{3}}}{\rm{y}} - 2{{\rm{x}}^{\rm{4}}}{{\rm{y}}^{\rm{3}}}
\end{array}\)