令X=0代入第二式核肢好 f(0-y)=f(0)-y(2*0-y+1)化改铅简得饥物 f(-y)=1-y(1-y)f(-y)=y^2-y+1令-y=x 代入上式 f(x)=(-x)^2-(-x)=1 f(x)=x^2+x=1