1) B
x+y=12
xy=35
По т.Виета
x1=7 y1=12-7=5
x2=5 y2=12-5=7
2) A B
x+y=4
y+xy=6
x=4-y
y+(4-y)y=6
y+4y-y²-6=0
y²-5y+6=0
D=25-24=1
√D=1
y1=(5+1)/2=3 x1=4-3=1
y2=(5-1)/2=2 x2=4-2=2
3)
y=x²
y=x+2
x+2=x²
x²-x-2=0
D=1+8=9
√D=3
x1=(1+3)/2= 2 y1=2+2=4
x2=(1-3)/2= -1 у2=2-1=1