f(2X-1)=4X^2-2X
设T=2X-1
X=(T+1)/2
f(t)=4((t+1)/2)^2-2((t+1)/2)=(t+1)^2-2(t+1)=t^2+2t+1-2t-2=t^2-1
f(x)=x^2-1