вправа 1222 гдз 7 клас алгебра Мерзляк Полонський
7 клас ➠ алгебра ➠ Мерзляк Полонський
Вправа 1222
Відповідь:
\begin{equation}1)+\left\{\begin{matrix}
3x+7y=1, |\cdot 2\\6y-5x=16;
\end{matrix}\right.
\end{equation}
\begin{equation}\left\{\begin{matrix}
x+20y=18,\\6y-5x=16;
\end{matrix}\right.
\end{equation}
\begin{equation}\left\{\begin{matrix}
x=18-20y,\\6y-5\left ( 18-20y \right )=16;
\end{matrix}\right.
\end{equation}
\begin{equation}\left\{\begin{matrix}
x=18-20y,\\6y-90+100y=16;
\end{matrix}\right.
\end{equation}
\begin{equation}\left\{\begin{matrix}
x=18-20y,\\106y=106;
\end{matrix}\right.
\end{equation}
\begin{equation}\left\{\begin{matrix}
x=-2,\\y=1;
\end{matrix}\right.
\end{equation}
\begin{equation}2)+\left\{\begin{matrix}
3x-5y=19, |\cdot 3\\ 2x+3y=0;|\cdot 5
\end{matrix}\right.
\end{equation}
\begin{equation}\left\{\begin{matrix}
9x-15y=57,\\10x+15y=0;
\end{matrix}\right.
\end{equation}
\begin{equation}\left\{\begin{matrix}
19x=57,\\2x+3y=0;
\end{matrix}\right.
\end{equation}
\begin{equation}\left\{\begin{matrix}
x=3,\\3y=-6;
\end{matrix}\right.
\end{equation}
\begin{equation}\left\{\begin{matrix}
x=3,\\y=-2;
\end{matrix}\right.
\end{equation}
\begin{equation}3)\left\{\begin{matrix}
3\left ( 2a-1 \right )+6\left ( 7-b \right )=51,\\2\left ( a+6 \right )-7\left ( 1+6b \right )=49;
\end{matrix}\right.
\end{equation}
\begin{equation}\left\{\begin{matrix}
6a-3+42-6b=51,\\2a+12-7-42b=49;
\end{matrix}\right.
\end{equation}
\begin{equation}\left\{\begin{matrix}
6a-6b=12,\\2a-42b=44;
\end{matrix}\right.
\end{equation}
\begin{equation}\left\{\begin{matrix}
a-b=2,\\a-21b=22;
\end{matrix}\right.
\end{equation}
\begin{equation}\left\{\begin{matrix}
a=2+b,\\2+b-21b=22;
\end{matrix}\right.
\end{equation}
\begin{equation}\left\{\begin{matrix}
a=2+b,\\-20b=20;
\end{matrix}\right.
\end{equation}
\begin{equation}\left\{\begin{matrix}
a=1,\\b=-1;
\end{matrix}\right.
\end{equation}
\begin{equation}4)\left\{\begin{matrix}
\frac{3x-2y}{4}-\frac{4x+5}{3}=-5,|\cdot 12\\\frac{6x-5y}{2}+\frac{2x+y}{5}=9;|\cdot 10
\end{matrix}\right.
\end{equation}
\begin{equation}\left\{\begin{matrix}
3\left ( 3x-2y \right )-4\left ( 4x+5 \right )=-60,\\5\left ( 6x-5y \right )+2\left ( 2x+y \right )=90;
\end{matrix}\right.
\end{equation}
\begin{equation}\left\{\begin{matrix}
9x-6y-16x-20=-60,\\30x-25y+4x+2y=90;
\end{matrix}\right.
\end{equation}
\begin{equation}\left\{\begin{matrix}
-7x-6y=-40,\\34x-23y=90;
\end{matrix}\right.
\end{equation}
\begin{equation}\left\{\begin{matrix}
x=\frac{40-6y}{7},\\\frac{34\left ( 40-6y \right )}{7}-23y=90;
\end{matrix}\right.
\end{equation}
\begin{equation}\left\{\begin{matrix}
x=\frac{40-6y}{7},\\\frac{34\left ( 40-6y \right )}{7}-\frac{161y}{7}=\frac{630}{7};
\end{matrix}\right.
\end{equation}
\begin{equation}\left\{\begin{matrix}
x=\frac{40-6y}{7},\\1360-204y-161y=630;
\end{matrix}\right.
\end{equation}
\begin{equation}\left\{\begin{matrix}
x=\frac{40-6y}{7},\\-365y=-730;
\end{matrix}\right.
\end{equation}
\begin{equation}\left\{\begin{matrix}
x=4,\\y=2.
\end{matrix}\right.
\end{equation}