假设y = f(x)^g(x),lny = g(x)lnf(x),y'/y = [g(x)/f(x)]·f(x) + g'(x)lnf(x)
∴y' = [f(x)^g(x)]·{[g(x)/f(x)]·f(x) + g'(x)lnf(x)}