Question

求导数f(x)=8/(x^2+4)

Answer 1

f'(x)=8(x^2+4)^(-1)

=-8(x^2+4)^(-2)(2x)

=-16x/(x^2+4)^2

f"(x)=-16*[(x^2+4)^2-2(x^2+4)(2x)]/(x^2+4)^4

=-16(x^2+4-4x)/(x^2+4)^3

=-16(x-2)^2/(x^2+4)^3