令t=x-1f(t)=[at^2+bt+c-√((t+1)^2+3)]f(0)=c-2f'(t)=2at+b-1/2*[(t+1)^2+3]^(-1/2)*2(t+1)=2at+b-[(t+1)^2+3]^(-1/2)*(t+1)f'(0)=b-1/2f''(t)=2a-[(t+1)^2+3]^(-1/2)+1/2*[(t+1)^2+3]^(-3/2)*2(t+1)*(t+1)f''(0)=...
或者就是0/0型极限分子分母分别求导需要连续计算2次3个分母在x-1时都是0值也是上面那个步骤还是那个答案