6. Решите уравнение: a) (x+0,1)(x-1/6)(x+3,9)=0; б) 5x(4x-0,2)=0; в) 6,3x-0,7x²=0; г) 1/5*u²-9/20=0; д) 1,4a²-4,2=0; e) 8y+0,4y²=0.

а) (x+0,1)(x-1/6)(x+3,9) = 0 x + 0.1 = 0 или x - 1/6 = 0 или x + 3.9 = 0 x = -0.1 или x = 1/6 или x = -3.9 б) 5x(4x - 0.2) = 0 5x = 0 или 4x - 0.2 = 0 x = 0 или 4x = 0.2 x = 0 или x = 0.05 в) 6.3x - 0.7x² = 0 x(6.3 - 0.7x) = 0 x = 0 или 6.3 - 0.7x = 0 x = 0 или 0.7x = 6.3 x = 0 или x = 9 г) 1/5 * u² - 9/20 = 0 1/5 * u² = 9/20 u² = 9/20 * 5 u² = 9/4 u = ±3/2 д) 1.4a² - 4.2 = 0 1.4a² = 4.2 a² = 3 a = ±√3 e) 8y + 0.4y² = 0 y(8 + 0.4y) = 0 y = 0 или 8 + 0.4y = 0 y = 0 или 0.4y = -8 y = 0 или y = -20 Ответ: а) x = -0.1, x = 1/6, x = -3.9; б) x = 0, x = 0.05; в) x = 0, x = 9; г) u = ±3/2; д) a = ±√3; e) y = 0, y = -20.