Question

Система 3x+y=2, x+2y=-6 *
2 бали
(-2;-4)
(-2;4)
(2;-4)
(2;4)

Answer 1

Ответ:

3x+y=2

x+2y=-6

y=2-3x

x+2y=-6

x+2(2-3x)=-6

x+4-6x=-6

x-6x=-6-4

-5x=-10

x=-10÷-5

x=2

y=2-3×2

y=-4

ответ:

(x;y)=(2;-4)

Answer 2

$\begin{cases}3x + y = 2 \\ x + 2y = - 6 \mid\!\times ( - 3 ) \end{cases} \\ \begin{cases}3x + y = 2 \\ - 3x - 6y = 18 \end{cases} \\ \overline{ \qquad \qquad \qquad} \\ - 5y = 20 \\ y = - 4 \\ \overline{ \qquad \qquad \qquad} \\ 3x + ( - 4) = 2 \\ 3x - 4 = 2 \\ 3x = 6 \\ x = 2$

Ответ: (2;-4)