Question

已知f(2x+3)=x^2－2x－3,则f(x－1)=

Answer 1

y=2x+3 x=(y-3)/2 f(y)=(y-3)^2/4-(y-3)-3=(y^2-6y+9)/4-(y-3)-3=(y^2-10y+9)/4 f(x-1)=[(x-1)^2-10(x-1)+9]/4=(x^2-12x+20)/4