836. Найдите корень уравнения: a) (x-5)^2-x^2 = 3; б) (2у + 1)^2-4y^2 = 5; в) 9х2-1-(3x - 2)^2 = 0; г) х + (5x + 2)² = 25(1 + x²).

a) (x-5)^2 - x^2 = 3 x^2 - 10x + 25 - x^2 = 3 -10x + 25 = 3 -10x = -22 x = 2.2 б) (2у + 1)^2 - 4y^2 = 5 4y^2 + 4y + 1 - 4y^2 = 5 4y + 1 = 5 4y = 4 y = 1 в) 9х^2 - 1 - (3x - 2)^2 = 0 9x^2 - 1 - (9x^2 - 12x + 4) = 0 12x - 5 = 0 12x = 5 x = 5/12 г) х + (5x + 2)² = 25(1 + x²) x + 25x^2 + 20x + 4 = 25 + 25x^2 21x + 4 = 25 + 25x^2 - 25x^2 21x = 21 x = 1