привести к общему знаменателю (x <> y ___ x <> -y ___ y <> 0 ___ <>===не равно)
12(x^2-y^2) = 48(xy-y^2) + 36(xy+y^2) ___ 48(x-y) + 48(x+y) = 7(x^2-y^2)
x^2-y^2 = 4xy - 4y^2 + 3xy + 3y^2 ___ 48x - 48y + 48x + 48y = 7(x^2-y^2)
x^2 = 7xy ___ 96x = 7(x^2-y^2)
x^2 - 7xy = 0 ___ 96x = 7(x^2-y^2)
x(x - 7y) = 0 ___ 96x = 7(x^2-y^2)
x = 0 ___ 0 = -7y^2 => y = 0---не удовлетворяет ОДЗ
x = 7y ___ 96*7y = 7(49y^2-y^2) => 96*y = 48y^2 => 2y = y^2 => y=2 (y не равно 0) => x=14