Предмет: Алгебра, автор: artemasin18

решите систему уровнений методом алгебраического сложения 3x+4y=-1 2x-5y=7

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Ответы

Автор ответа: sangers1959
1

Объяснение:

\left \{ {{3x+4y=-1\ *5} \atop {2x-5y=7\ |*4}} \right. \ \ \ \ \left \{ {{15x+20y=-5} \atop {8x-20y=28}} \right. .

Суммируем эти уравнения:

23x=23\ |:23\\x=1\ \ \ \ \Rightarrow\\2*1-5y=7\\2-5y=7\\5y=-5\ |:5\\y=-1.

Ответ: (1;-1).

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