3
x²+y²=9
x²+y=3
отнимем
y²-y=6
y²-y-6=0
y1=y2=1 U y1*y2=-6
y1=-2⇒x²=5⇒x=+-√5
y2=3⇒x²=0⇒x=0
(√5;-2);(-√5;-2);(0;3)
4
1/2x²=3x-4
x²-6x+8=0
x1+x2=6 U x1*x2=8
x1=2⇒y1=2
x2=4⇒y2=8
(2;2);(4;8)
5
1/x-1/y=1/12⇒12y-12x=1
5x-y=18⇒y=5x-18
60x-216-12x=5x²-18x
5x²-66x+216=0
D=4356-4320=36
x1=(66-6)/10=6⇒y1=30-18=12
x2=(66+6)/10=7,2⇒y2=36-18=18
(6;12);(7,2;18)