OA*OB=(x1+y1i)*(x2+y2i)
=(x1+(kx1-1)i)*(x2+(kx2-1)i)
=(1-k^2)x1*x2+k(x1+x2)-1+[2kx1x2-(x1+x2)]i
=(1-k^2)/k^2+k*(2k+4)/k^2-1+[2k/k^2-(2k+4)/k^2]i
=(4k+1)/k^2-(4/k^2)i
将y=kx-1代入抛物线方程,可得x1*x2及x1+x2的含k代数式,就可得到以上结论
当k=2时,OA*OB=2.25-i
第二问问法有错误