y=kx+m

x 1+x2=(-2km)/(a^2k^2+b^2),x 1x2=a^2(m^2-b^2)/(a^2k^2+b^2)，

The unary quadratic equation is (a 2k 2+b 2) x 2+2mka 2x+a 2 (m 2-b 2) = 0.

Just remember the formula.