设2X+1=T
X=(T-1)/2
f(T)=[(T-1)/2]²+3(T-1)/2+2
=T²/4-T/2+1/4+3T/2-3/2+2
=T²/4+T+3/4
f(x)=x²/4+x+3/4
f(3x)=(3x)²/4+3x+3/4=9x²4+3x+3/4
设2X+1=T
X=(T-1)/2
f(T)=[(T-1)/2]²+3(T-1)/2+2
=T²/4-T/2+1/4+3T/2-3/2+2
=T²/4+T+3/4
f(x)=x²/4+x+3/4
f(3x)=(3x)²/4+3x+3/4=9x²4+3x+3/4