If (6, 9) is one end of double ordinate of ${\mathrm{x}}^2=4\mathrm{y}$ then equation of double ordinate is

$$\begin{gathered} \mathrm{Given} \mathrm{parabola} {\mathrm{x}}^2=4\mathrm{y} \\ \Rightarrow 4\mathrm{a}=4 \\ \Rightarrow \mathrm{a}=1 \end{gathered}$$

End points of double ordinate are (6,9) and (-6,9)

Double coordinate parallel to x-axis and it's equation is $\mathrm{y}=9$