（1）、曲线C1,C2开口向上,∵C2-C1=x^2-3x+3=(x-3/2)^2+3/4 〉0,∴C1,C2没有交点且C2在C1的内部.
（2）、四个交点A(x1,y1),B(x2,y2),C(x3,y3),D(x4,y4),
AB=√（y2-y1)^2+(x2-x1)^2=√(kx2+m-kx1-m)^2+(x2-x1)^2=√(k^2+1)(x2-x1)
同理CD=√(k^2+1)(x4-x3) ∴AB-CD=√(k^2+1)(x2-x1-x4+x3)
∵y3-y2=2x3^2-3x3+3-2x2^2+3x2-3=2x3^2-2x2^2-3x3+3x2=kx3+m-kx2-m=k(x3-x2)
∴2(x3+x2)(x3-x2)-3(x3-x2)=k(x3-x2) ∴2(x3+x2)=k+3 x3+x2=(k+3)/2
同理y4-y1=x4^2-x1^2=(x4+x1)(x4-x1)=kx4+m-kx1-m=k(x4-x1)
x4+x1=k
∴AB-CD=√(k^2+1)(x2-x1-x4+x3)=√(k^2+1)(k/2+3/2-k)=√(k^2+1)(3/2-k/2)
∴k为定值时,AB-CD也为定值.
（3）、AB+CD=√(k^2+1)(x2-x1+x4-x3)
k=1,x^2=x+m (x-1/2)^2=m+1/4 x4-x1=2√(m+1/4)=√(4m+1)
2x^2-3x+3=x+m 2(x-1)^2=m-1 x2-x3=-2√（m-1)/2=-√（2m-2)
AB+CD=√(8m+2)-√(4m-4)
√是根号,第三个是不是求AB-CD哦!