вправа 733 гдз 7 клас алгебра Мерзляк Полонський

Відповідь: \begin{equation}1)\left ( 5x-y^{2} \right )\left ( 5x+y^{2} \right )-\end{equation} \begin{equation}-2\left ( 15x-7y^{2} \right )-40=\end{equation} \begin{equation}=25x^{2}-y^{4}-30x+\end{equation} \begin{equation}+14y^{2}-40=\end{equation} \begin{equation}=25x^{2}-30x+9-( y^{4}-\end{equation} \begin{equation}-14y^{2}+49)=\end{equation} \begin{equation}=\left ( 5x-3 \right )^{2}-\left ( y^{2}-7 \right )^{2}=\end{equation} \begin{equation}=\left ( 5x-3-\left ( y^{2}-7 \right ) \right )\end{equation} \begin{equation}\left ( 5x-3+\left ( y^{2}-7 \right ) \right )=\end{equation} \begin{equation}=\left ( 5x-y^{2}+4 \right )\left ( 5x+y^{2}-10 \right );\end{equation} 2) (3m - 2n)(12m + 5n) +
+ 3m(3n + 4) - 2(3n² - 20n + 12) =
= 36m² - 9mn - 10n² +
+ 9mn + 12m - 6n² + 40n - 24 =
= (36m² + 12m + 1) - (16n² - 40n + 25) =
= (6m + 1)² - (4n - 5)² =
= (6m + 1 - (4n - 5))(6m + 1 + (4n - 5)) =
= (6m - 4n + 6)(6m + 4n - 4) =
= 4(3m - 2n + 3)(3m + 2n - 2).