f(0-y)=f(0)-y(-y+1)f(-y)=1+y^2-y令-y=x得f(x)=1+(-x)^2-(-x)=x^2+x+1
当x=y时,f(0)=f(x)-x(x-1), 即f(x)-x^2-x=1,得出f(x)=x^2+x+1