Answer
The general equation of a parabola is
which represents parabola opening along the positive x-axis and vertex at the origin.
Second equation of the parabola is
which represents parabola opening in negative x-axis and vertex at origin.
3rd Equation of parabola is
which represents parabola opening along the positive y-axis and vertex at the origin.
4th equation of the parabola is
which represents parabola opening along negative y-axis and vertex at the origin.
Hence, the 4th equation represents Equation 2 which is
, and parabola opens down and has a negative y-intercept.