A)x=7-y
(7-y)²+y²=25
y²-14y+49+y²-25=0
2y²-14y+24=0
y²-7y+12=0
y1+y2=7 U y1*y2=12
y1=3⇒x1=4
y2=4⇒x2=3
(4;3) (3;4)
b)x=2-y
(2-y)²*y²-(2-y)*y=12
(4-4y+y²)*y²-2y+y²-12=0
y^4-4y³+5y²-2y-12=0
(y+1)(y-3)(y²-2y+4)=0
y1=-1⇒x1=3
y2=3⇒x2=-1
y²-2y+4=0
D=4-16=-12<0нет решения<br>(3;-1) (-1;3)