(1)f(-x)=-f(x)所以為奇函數(shù)
f'(x)=(1/3)x^(-2/3)+(1/3)x^(-4/3)
令f'(x)=0
x^(-2/3)+x^(-4/3)=0
x^(-2/3)(1+x^2)=0
則函數(shù)為增函數(shù)
(2)-5f(2)g(2)=-5*(18-1)/(3^√2)=-85/3^√2
f(9)=(81-1)/(3^√9)=80/(3^√9)
-5f(3)g(3)=[-5(27-1)/(3^√3)](3^√3-1)
f(9)-5f(3)g(3)=80/3^√9-130/(27-3^√3)