f(x-1)=x^2-2x-3令 x-1=t x=t+1则f(t)=(t+1)^2-2(t+1)-3 =(t+1)(t+1-2)-3 =(t+1)(t-1)-3 =t^2-1-3 =t^2-4令t=x则f(x)=x^2-4
因为f(x-1)=x²-2x-3,所以f(x)=f(x+1-1)=(x+1)²-2(x+1)-3=x²+1-2x-2x-2-3=x²-4x-4,本体突破点是x=(x+1)-1