Question

ребят хелп 2 уравнения , срочно!!

Answer 1

$1) left { {{3x+y=7} atop {9x-4y=-7}} right. \ left { {{y=7-3x} atop {9x-4cdot (7-3x)=-7}} right. \ left { {{y=7-3x} atop {9x-28+12x=-7}} right. \ left { {{y=7-3x} atop {9x+12x=-7+28}} right. \ left { {{y=7-3x} atop {21x=21}} right. \ left { {{y=7-3cdot1} atop {x=1}} right. \ left { {{y=4} atop {x=1}} right.$
Ответ. (1;4)
$2) left { {{x-3y=6} atop {2y-5x=-4}} right. \ left { {x=3y+6} atop {2y-5cdot (3y+6)=-4}} right. \ left { {{x=3y+6 atop {2y-15y-30=-4}} right. \ left { {{x=3y+6} atop {-13y=26}} right. \ left { {{x=3y+6} atop {y=-2}} right. \ left { {{x=3cdot(-2)+6} atop {y=-2}} right. \ left { {{x=0} atop {y=-2}} right.$
Ответ. (0; -2)