f(x)=-1/4x^4 + x^3, х0 = -1;
k = tga = f'(x);
f'(x) = (-1/4x^4 + x^3)' = -x^3 + 3x^2;
f'(x0) = f'(-1) = -(-1)^3 + 3 * (-1)^2 = 1 + 3 = 4.
ответ: 4.
