解:f(x)=x²-3x则 f(x-1)=(x-1)²-3(x-1)=x²-2x+1-3x+3=x²-5x+4
f(x-1)=(x-1)^2-3(x-1)=x²-2x+1-3x+3=x²-5x+4
f(x-1)=(x-1)^2-3(x-1)=x^2-5x+4
