What r the equations of tangents :-1- parallel to x-axis .2- parallel to y-axis.3-not parallel to x or y -axes.4- at origin.5-relation to parabola.....

A line parallel to the x-axis will have slope m=0. So you need to take the first derivative, and set it equal to zero to solve for the x values at which the slope of the tangent to your curve is zero.

Using each solution x0, find its corresponding y-coordinate(s) using your original equation. For point (x0,y0) on a line, the corresponding equation of the line is given by
y−y0=m(x−x0)
In your case, slope being zero, your equation(s) will be given by y=y0.