If the line `l x+m y+n=0` touches the parabola `y^2=4a x ,` prove that `ln=a m^2`

Explanation

The x-coordinates of the points of intersection of the line `lx+my+n=0`





or `y=-((lx+n)/(m))` and the parabola `y^2=4ax` are roots of the equation.





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