Write an equation of an ellipse in standard form with the center at the origin and with the given characteristics.

vertex at (–5, 0) and co-vertex at (0, 4)

The equation of an ellipse in standard form with the center at the origin is:

x^2/a^2 + y^2/b^2 = 1

where (a,b) are the lengths of the semi-major and semi-minor axes, respectively.

Given that the vertex is at (-5, 0) and the co-vertex is at (0, 4), we can determine that a = 5 and b = 4.

Therefore, the equation of the ellipse in standard form is:

x^2/5^2 + y^2/4^2 = 1

Simplifying:

x^2/25 + y^2/16 = 1

The equation of the ellipse in standard form with the center at the origin is:

x^2/25 + y^2/16 = 1