Помогите решить задачи с Высшей Математике

ОТВЕТ
для зад.3:
x1= 3, y1= -9
x2 = -1, y2 = 5
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y = x^3/3 - x^2 - 3x,
dy/dx = x^2 - 2x - 3,
dy/dx =0, x^2 - 2x - 3 = 0,
D = 4 + 12 = 16, x1,2 = (2 +,-4)/2,
x1= 3, x2 = -1
y1= x^3/3 - x^2 - 3x =3^3/3 - 3^2 - 3*3 = 9 - 9 -9 = -9
y2 = x^3/3 - x^2 - 3x = (-1)^3 - (-1)^2 - 3*(-1) = -1 - 1 + 3 = 5