(3x+y)(x+y)-4 (x-y)=3x2+3xy+xy+y2-4xy+4y2=3x2+4xy-4xy+5y2=3x2+5y2.
3x² - 7x + 4 = 0
D = b² - 4ac = 49 - 4×3×4 = 49 - 48 = 1
x1 = ( 7 + 1) / 6 = 8/6 = 4/3 = 1 1/3
x2 = ( 7 - 1) /6 = 1
(x-5)^2+(y-3)^2=R^2
(1-5)^2+(0-3)^2=R^2
R^2=25
R=5
ответ (x-5)^2+(y-3)^2=25