The focus of parabola  and directrix .

The directricx is , the parabola is horizontal.

Focus of the parabola is left of the directrix, then the parabola is opens left.

Standard form of horizontal parabola with focus  .

Where center is , focus is  and directrix is .

In this case 

And .

Add the equations (1) and (2).

.

Substitute in equation (2).

Substitute the values ,  and  in standard form.

.

The parabola equation is .