Chapter 13 - Section 13.3 - Solving Nonlinear Systems of Equations - Exercise Set - Page 948: 25

${(-\sqrt 3, 0), (\sqrt 3,0)}$

$3x^2+y^2=9$ $3x^2-y^2=9$ $3x^2+y^2+3x^2-y^2=9+9$ $6x^2=18$ $6x^2/6=18/6$ $x^2=3$ $\sqrt {x^2} =\sqrt 3$ $x =±\sqrt 3$ $3x^2+y^2=9$ $3*3+y^2=9$ $9+y^2=9$ $9+y^2-9=9-9$ $y^2=0$ $\sqrt {y^2} =\sqrt 0$ $y=0$