Решите систему x-y=- 7 xy- 4y+x- 4=0

Question

Решите систему x-y=- 7
xy- 4y+x- 4=0

Answer 1

X=y-7
y²-7-4y+y-7-4=0
y²-3y-18=0
D=(-3)²-4*1*(-18)=9+72=81
y₁=(7+√81)/2=8
y₂=(7-√81)/2=-1
x₁=8-7=1
x₂=-1-7=-8