3
{2(x+y)²-7(x+y)+3=0 U {2x-3y=-1
(x+y)=a
2a²-7a+3=0
D=49-24=25
a1=(7-5)/4=0,5⇒x+y=0,5⇒x=0,5-y
2(0,5-y)-3y=-1
1-2y-3y=-1
-5y=-2
y=0,4
x=0,5-0,4=0,1
a2=(7+5)/4=3⇒x+y=3⇒x=3-y
2(3-y)-3y=-1
6-2y-3y=-1
-5y=-7
y=1,2
x=3-1,2=1,8
(0,1;0,4);(1,8;1,2)
4
{2x²+2y²+x-y-4=0/*3⇒6x²+6y²+3x-3y-12=0
{3x²+3y²+2x-y-7=0/*(-2)⇒-6x²-6y²-4x+2y+14=0
прибавим
-x-y+2=0
x=2-y
2(2-y)²+2y²+2-y-y-4=0
8-8y+2y²+2y²+2-y-y-4=0
4y²-10y+6=0
D=100-96=4
y1=(10-2)/8=1⇒x1=2-1=1
y2=(10+2)/8=1,5⇒x2=2-1,5=0,5
(1;1);(0,5;1,5)