解法一：令2x+1=t,则x=(t-1)/2f(t)=(t-1)²/4-(t-1)f(3)=1-2=-1解法二：f(2x+1)=x2-2x 令y=2x+1x=(y-1)/2f(y)=[(y-1)/2]²-(y-1)=y²/4-3y/2+5/4所以,f(x)=x²/4+3x/2+5/4f(3)=f(2*1+1)=1²-2*1...