答案：f'(1)的值为3
f(x+y)=f(x)+f(y)+2xy,
对两边求,x,y的导数；
f'(x+y)(x的导）+f'(x+y)(y的导）=f'(x)+f'(y)+2y+2x
再领x=0;y=1;
就搞定了!