f(x)' = ((x^3 – 4x)^4)’ = (x^3 – 4x)’ * ((x^3 – 4x)^4)’ = ((x^3)’ – (4x)’) * ((x^3 – 4x)^4)’ =
(3 * x^2 – 4) * 4 * (x^3 – 4x)^3 = 4 * (3x^2 – 4) * (x^3 – 4x)^3.
f(x)' = ((x + 1) / (x^2 + 1))’ = ((x + 1)’ * (x^2 + 1) - (x + 1) * (x^2 + 1)’) / (x^2 + 1)^2 = (((x)’ + (1)’) * (x^2 + 1) - (x + 1) * ((x^2)’ + (1)’)) / (x^2 + 1)^2 = ((1 + 0) * (x^2 + 1) - (x + 1) * (2x + 0)) / (x^2 + 1)^2 = (x^2 + 1 - 2x^2 - 2x) / (x^2 + 1)^2 = (-x^2 - 2x + 1) / (x^2 + 1)^2.
f(x)' = ((x^2) / (x^2 + 1))’ = ((x^2)’ * (x^2 + 1) - (x^2) * (x^2 + 1)’) / (x^2 + 1)^2 = ((x^2)’) * (x^2 + 1) - (x^2) * ((x^2)’ + (1)’)) / (x^2 + 1)^2 = (2x * (x^2 + 1) - (x^2) * (2x + 0)) / (x^2 + 1)^2 = (2x^3 + 2x - 2x^3) / (x^2 + 1)^2 = 2x / (x^2 + 1)^2.
f(x)' = ((x^3) / (x^2 + 5))’ = ((x^3)’ * (x^2 + 5) - (x^3) * (x^2 + 5)’) / (x^2 + 5)^2 = ((x^3)’) * (x^2 + 5) - (x^3) * ((x^2)’ + (5)’)) / (x^2 + 5)^2 = (3x^2 * (x^2 + 5) - (x^3) * (2x + 0)) / (x^2 + 5)^2 = (3x^4 + 15x^2 - 2x^4) / (x^2 + 5)^2 = (x^4 + 15x^2) / (x^2 + 5)^2.