1)2xy-y=7
x-5y=2⇒x=5y+2
10y²+4y-y-7=0
10y²+3y-7=0
D=9+280=289
y1=(-3-17)/20=-1⇒x1=-5+2=-3
y2=(-3+17)/20=0,7⇒x2=3,5+2=5,5
(-3;-1);(5,5;0,7)
2)2x²-xy=33
4x-y=17⇒y=4x-17
2x²-4x²+17x-33=0
2x²-17x+33=0
D=289-264=25
x1=(17-5)/4=3⇒y1=12-17=-5
x2=(17+5)/4=5,5⇒y2=22-17=5
(3;-5);(5,5;5)
3)x²+2y=18
3x=2y
x²+3x-18=0
x1+x2=-3 u x1*x2=-18
x1=-6⇒y1=1,5*(-6)=9
x2=3⇒y2=1,5*3=4,5
(-6;-9);(3;4,5)