If the vertex of the parabola $y = x^2 - 8x + c$ lies on the $x$-axis,then the value of $c$ is:

Suppose a parabola passes through $(0,4), (1,9)$ and $(4,5)$ and has its axis parallel to the $y$-axis. Then the equation of the parabola is

The vertex and the focus of the parabola $2y^2 + 5x - 6y + 1 = 0$ are respectively

The vertex of a parabola is the point $(a, b)$ and the latus rectum is of length $l$. If the axis of the parabola is along the positive direction of the $y$-axis,then its equation is

What is the equation of the directrix of the parabola $y^2 + 4y + 4x + 2 = 0$?

If a normal chord at a point $t$ on the parabola $y^2=4ax$ subtends a right angle at the vertex,then $t^2$ equals to