Find the equation of a parabola that satisfies the given condition:
Focus (6, 0), directrix is x = – 6

The focus is S(6, 0) which lies on x-axis.
The directrix is x + 6 = 0 which is a line parallel to y-axis i.e., perpendicular to x-axis.
∴   The parabola is of the standard form 
Also, focus (a, 0)  (6, 0) directrix x + a = 0 is x + 6 = 0  a = 6
Hence, the equation of the parabola is 
Alternative method:
Let line l be the directrix with equation x + 6 = 0
The focus is S (6, 0). Take a point  on the parabola.
From P, draw PM perpendicular on directrix l and join PS. By definition of parabola, PS = PM
                                      d = p
      
                                           
Squaring both sides, we get

Hence, the locus of P i.e., the equation of parabola is