令a=g(x)=1-2xx=(1-a)/2所以f(a)=(1-x^2)/x^2=1/x^2-1=1/[(1-a)^2/4]-1=4/(a^2-2a+1)-1所以f(x)=4/(x^2-2x+1)-1=(-x^2+2x+3)/(x^2-2x+1) 令g(x)=1-2x=0,x=1/2所以f(0)=(1-x^2)/x^2=1/x^2-1=1/(1/4)-1=3
令g(x)=t,则x=(1-t)/2f(t)=1/[(1-t)/2]^2-1=4/(t^2-2t+1)-1把t换成x即可