g(x+1/x)=(x+1/x)^2-2得g(x)=x^2-2
f(x+1/x)=(x+1/x)(x^2-1+1/x^2)=(x+1/x)[(x+1/x)^2-3]得f(x)=x*(x^2-3)
f(g(x))=(x^2-2)[(x^2-2)^2-3]