Решение:
(7x + 2y)² - (3x - y)(4x + 5y) = 49x² + 28xy + 4y² - 12x² - 15xy + 4xy + 5y² = 37x² + 9y² + 17xy
2-6x=6x+10-96
2-6x-6x-10+96=0
-12x+88=0
12x-88=0
12x=88
x=7.(3)
R^2=1^2+(-4)^2=17
(x-a)^2+(y-b)^2=R^2
x^2+y^2=17
√1,8/√12,8=√(1,8/12,8)=<span>√(18/128)=</span>√(36/256)=6/16=3/8.
Ответ: 2)