Answer
$(0, -2)$, $(0,2)$
Work Step by Step
$x^2+4y^2=16$
$x^2+y^2=4$
$x^2+4y^2-(x^2+y^2)=16-4$
$x^2+4y^2-x^2-y^2=12$
$3y^2=12$
$3y^2/3 =12/3$
$y^2=4$
$x^2+y^2=4$
$x^2+4=4$
$x^2=0$
$\sqrt {x^2} = \sqrt 0$
$x=0$
$y^2=4$
$\sqrt {y^2}=\sqrt 4$
$y=±2$
