Предмет: Алгебра, автор: Мистерхлеб

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Ответы

Автор ответа: 233334

1.а) $left { {{x+y=5,} atop {x-y=7;}} right. left { {{2x=12,} atop {x-y=7;}} right. left { {{x=6,} atop {6-y=7;}} right. left { {{x=6,} atop {y=-1}} right.$
Ответ:(6;-1)
б) $left { {{a-b=1,} atop {a+b=-5;}} right. left { {{2a=-4,} atop {a+b=-5;}} left { {{a=-2,} atop {-2+b=-5;}} right. left { {{a=-2,} atop {b=-3;}} right.$
в) $left { {{2n+m=5,} atop {2n-m=11;}} right. left { {{4n=16,} atop {2n-m=11;}} right. left { {{n=4,} atop {8-m=11;}} right. left { {{n=4,} atop {m=-3;}} right.$
2.а) $left { {{u+v=4,|*5} atop {3u-5v=20;}} right. left { {{5u+5v=20,} atop {3u-5v=20;}} right. left { {{8u=40,} atop {3u-5v=20;}} right. left { {{u=5,} atop {15-5v=20;}} right. left { {{u=5,} atop {v=-1;}} right.$
б) $left { {{3x-y=5,|*7} atop {2x+7y=11;}} right. left { {{21x-7y=35,} atop {2x+7y=11;}} right. left { {{23x=46,} atop {2x+7y=11;}} right. left { {{x=2,} atop {4+7y=11;}} right. left { {{x=2,} atop {y=1;}} right.$
в) $left { {{4m-5n=1,} atop {2m-3n=2;|*(-2)}} right. left { {{4m-5n=1,} atop {-4m+6n=-4;}} right. left { {{n=-3,} atop {2m+9=2;}} right. left { {{n=-3,} atop {m=-3,5}} right.$
3.а) $left { {{2x+3y=-1,|*3} atop {3x+5y=-2;|*(-2)}} right. left { {{6x+9y=-3,} atop {-6x-10y=4;}} right. left { {{y=-1,} atop {3x-5=-2;}} right. left { {{y=-1,} atop {x=1;}} right.$
б) $left { {{2n-3d=-1,|*3} atop {3n+4d=24;|*(-2)}} right. left { {{6n-9d=-3,} atop {-6n-8d=-48;}} right. left { {{d=3,} atop {3n+12=24;}} right. left { {{d=3,} atop {n=4;}} right.$
в) $left { {{2a+3b=0,|*2} atop {7a-2b=-25;|*3}} right. left { {{4a+6b=0,} atop {21a-6b=-75;}} right. left { {{a=-3,} atop {-21-2b=-25;}} right. left { {{a=-3,} atop {b=2;}} right.$