x²+(x+t)²=1/2t²+2t-1x²+x²+2tx+t²=1/2t²+2t-1x²+tx+1/4t²-t+1/2=0判别式=t²-4*(1/4t²-t+1/2)=4t-2当4t-2＞0,即t＞1/2时,有两个不相等的实数根；当4t-2=0,...