The correct option is A 2x+y−18=0
Given equation of parabola is y2=6x
∴2ydydx=6
Given y-coordinate =6
⇒x=6
So, the point is (6,6)
Slope of tangent to the parabola at (6,6) is 12
So, slope of normal is -2.
Equation of normal at (6,6) is
y−6=−2(x−6)
⇒y−6=−2x+12
⇒y+2x−18=0