∵f'(1)是常数
∴f(x)=x^2+2xf'(1)
f'(x)=2x+2f'(1)
f'(1)=2*1+2f'(1)
f'(1)=-2
f(x)=x^2+2x*(-2)
=x^2-4x
f'(x)=2x-4
f'(0)=-4