∵方程x2+2kx+k2-2k+1=0的两个实数根，∴△=4k2-4（k2-2k+1）≥0，解得 k≥12．∵x12+x22=4，∴x12+x22=x12+2x1•x2+x22-2x1•x2=（x1+x2）2-2x1•x2=4，又∵x1+x2=-2k，x1•x2=k2-2k+1，代入上式有4k2-2（k2-2k+1）...