Question

Помогите пожалуйста

Answer 1

$2.5x^3 - 2.5x^2 - 30x = 0\\2.5x(x^2 - x - 12) = 0\\x = 0\\x^2 - x - 12 = 0\\D = 49\\x_1 = 4; x_2 = -3\\x = -3; x=0; x=4$