Question

Помогите решить, и объясните как решать срочно!

Answer 1

a)
$left { {{x+y=5} atop {3x+y=7}} right. \ left { {{y=5-x} atop {3x+5-x=7}} right. \ left { {{y=5-x} atop {2x=2}} right. \ left { {{x=1} atop {y=4}} right.$
Проверка:
$left { {{1+4=5} atop {3*1+4=7}} right.$
б)
$left { {{x-y=0} atop {x-3y=6}} right. \ left { {{y=x} atop {-2x=6}} right. \ left { {{x=-3} atop {y=-3}} right.$
Проверка:
$left { {{-3-(-3)=0} atop {-3-3*(-3)=6}} right.$
в)
$left { {{y-x=-3} atop {2x+y=9}} right. \ left { {{y=x-3} atop {2x+x-3=9}} right. \ left { {{y=x-3} atop {3x=12}} right. \ left { {{x=4} atop {y=1}} right.$
Проверка:
$left { {{1-4=-3} atop {2*4+1=9}} right.$

Answer 2

Умница!