Question 438558
Hmm..."16x squared + 4y squared = 25"

That's an ellipse,  {{{16x^2 + 4y^2 = 25}}}
<==> {{{x^2/(25/16) + y^2/(25/4) = 1}}} in standard form.

There are two lines of symmetry,namely x = 0 and y = 0.

The domain can be gotten from the minor axis, which is along the x-axis:
{{{sqrt(25/16) = 5/4}}}. Hence the domain is [-5/4, 5/4].
The range can be gotten from the major axis, which is along the y-axis:
{{{sqrt(25/4) = 5/2}}}. Hence the range is [-5/2, 5/2].

{{{graph( 300, 200, -5, 5, -5, 5, sqrt(25 - 16x^2)/2, -sqrt(25 - 16x^2)/2)}}}