Question

1511(4) 1512 (4) решите систему уравнений способом подстановки

Answer 1

$\begin{cases}\frac{7x}{3}-\frac{y}{9}=4|*9\\\frac{8x}{5}-\frac{y}{30}=3|*30\end{cases}\ \textless \ =\ \textgreater \ \begin{cases}21x-y=36=\ \textgreater \ y=21x-36\\48x-y=90\end{cases}\\48x-21x+36=90\\27x=54\\x=2\\y=21*2-36=42-36=6\\OTBET: (2;6)$

$\begin{cases}5(7x+2y)-11y=6(2x+y)+2\\33+3(6x-5y)=3(x+2y)-5y\end{cases}\ \textless \ =\ \textgreater \ \\\begin{cases}35x+10y-11y=12x+6y+2\\33+18x-15y=3x+6y-5y\end{cases}\ \textless \ =\ \textgreater \ \\\begin{cases}23x-7y=2=\ \textgreater \ y=\frac{23x-2}{7}\\15x-16y=-33\end{cases}\\15x-16*\frac{23x-2}{7}=-33|*7\\105x-16(23x-2)=-231\\105x-368x+32=-231\\-263x=-263\\x=1\\y=\frac{23-2}{7}=3\\OTBET: (1;3)$