Question

Очень нужна ваша помощь , решите линейное ур-ие методом подстановки
1)
$\left \{ {{3x-2y=4} \atop {7x-9y=5}} \right.$
2)
$\left \{ {{2x+5y=6} \atop {-4x-10y=8}} \right.$

Answer 1

$1)\left\{\begin{array}{l}3x-2y=4\\7x-9y=5\end{array}\right\ \ \left\{\begin{array}{l}y=\dfrac{3x-4}{2}\\7x-9(1,5x-2)=5\end{array}\right\ \ \left\{\begin{array}{l}y=1,5x-2\\-6,5x+18=5\end{array}\right\\\\\\\left\{\begin{array}{l}y=1,5x-2\\x=2\end{array}\right\ \ \left\{\begin{array}{l}y=1\\x=2\end{array}\right\ \ \ Otvet:\ \ (\, 2\, ;\, 1\, )\ .$

$2)\ \ \left\{\begin{array}{ccc}2x+5y=6\\-4x-10y=8\, |:2\end{array}\right\ \ \left\{\begin{array}{ccc}2x+5y=6\\-2x-5y=4\end{array}\right\ \ \left\{\begin{array}{l}2x=6-5y\\-(6-5y)-5y=4\end{array}\right\\\\\\\left\{\begin{array}{l}2x=6-5y\\-6+5y-5y=4\end{array}\right\ \ \left\{\begin{array}{l}2x=6-5y\\-6=4\ neverno\end{array}\right\ \ \ \Rightarrow \ \ \ net\ reshenij$