Срочно нужна!!!(ответы с полными решениями!!!)

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Срочно нужна!!!(ответы с полными решениями!!!)


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Алгебра (458 баллов) | 45 просмотров
Дан 1 ответ
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Правильный ответ
\left \{ {{x-y=7} \atop {xy=-12}} \right. \\ \left \{ {{x=7+y} \atop {(7+y)y=-12(*)}} \right.

(*) (7+y)y = -12
7y + y² + 12 = 0
y1 = -3        
y2 = -4       

1) \left \{ {{x=7+y} \atop {-3}} \right. \\ \left \{ {{x=7-3} \atop {-3}} \right. \\ \left \{ {{x=4} \atop {y=-3}} \right.
2) \left \{ {{x=7+y} \atop {y=-4}} \right. \\ \left \{ {{x=7-4} \atop {y=-4}} \right. \\ \left \{ {{x=3} \atop {y=-4}} \right.


\left \{ {{x-y=4} \atop {x^2-y^2=40}} \right. \\ \left \{ {{x=4+y} \atop {(4+y)^2-y^2=40(*)}} \right.
(*) (4 + y)² - y² = 40
16 + 8y + y² - y² = 40
8y = 24
y = 3

\left \{ {{x=4+y} \atop {y=3}} \right. \\ \left \{ {{x=7} \atop {y=3}} \right.


\left \{ {{x-y=4} \atop {xy=12}} \right. \\ \left \{ {{x=4+y} \atop {(4+y)y=12(*)}} \right.
(*) (4 + y)y = 12
4y + y² = 12
y² + 4y -12 = 0
y1 = 2
y2 = -6

1) \left \{ {{x=4+y} \atop {y=2}} \right. \\ \left \{ {{x=6} \atop {y=2}} \right.
2) \left \{ {{x=4+y} \atop {y=-6}} \right. \\ \left \{ {{x=-2} \atop {y=-6}} \right.


\left \{ {{x+y=5} \atop {xy=-14}} \right. \\ \left \{ {{x=5-y} \atop {(5-y)y=-14(*)}} \right.
(*) (5 - y)y = -14
y² - 5y -14 = 0
y1 = -2
y2 = 7
1) \left \{ {{x=5-y} \atop {y=-2}} \right. \\ \left \{ {{x=7} \atop {y=-2}} \right.
2) \left \{ {{x=5-y} \atop {y=7}} \right. \\ \left \{ {{x=-2} \atop {y=7}} \right.
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