Question

яка пара чисел є розв'язком системи 2x - 3y = -4
3x + 2y = 7?
А) (2;1) Б) (-1;-2) В) (-1;2) Г) (1;2)

Answer 1

$\begin{cases} 2x - 3y = - 4 \\ 3x + 2y = 7 \mid \times \: 1.5\end{cases} \\ \begin{cases}2x - 3y = - 4 \\ 4.5x + 3y = 10.5 \end{cases} \\ \\ 6.5x = 6.5 \\ x = 1 \\ \\ 2 \times 1 - 3y = - 4 \\ 2 - 3y = - 4 \\ 3y = 6 \\ y = 2 \\ \\ \boldsymbol{(1;2)}$

Ответ: Г.

Answer 2

$\left\{\begin{array}{ccc}2x-3y=-4 \ |\cdot2\\3x+2y=7 \ |\cdot 3\end{array}\right\\\\\\+\left\{\begin{array}{ccc}4x-6y=-8\\9x+6y=21\end{array}\right\\----------\\13x=13\\\\x=1\\\\2y=7-3x=7-3\cdot 1=4\\\\y=2\\\\Otvet:\boxed{(1 \ ; \ 2)}$