Answer
$(-2, -1)$, $(-2, 1)$, $(2, -1)$, $(2,1)$
Work Step by Step
$x^2-3y^2=1$
$4x^2+5y^2=21$
$x^2-3y^2=1$
$-4*(x^2-3y^2)=-4*1$
$-4x^2+12y^2=-4$
$-4x^2+12y^2+4x^2+5y^2=-4+21$
$12y^2+5y^2=17$
$17y^2=17$
$17y^2/17=17/17$
$y^2=1$
$x^2-3y^2=1$
$x^2-3*1=1$
$x^2-3=1$
$x^2-3+3=1+3$
$x^2=4$
$\sqrt {x^2} = \sqrt 4$
$x= ±2$
$y^2=1$
$\sqrt {y^2}=\sqrt 1$
$y=±1$
