1. Plug the points (x, y) into each equation properly.
2. You got rid of the 1 and didn't use it.
3. You'll need to solve a system of 2 equations to find a, b.
Check it yourself! It clearly has center (0,0). Do [itex](3, \sqrt{7})[/itex] and [itex]-\sqrt{3},3)[/itex] satisfy that equation? That is, are
[tex]\frac{3^2}{30}+ \frac{(\sqrt{7})^2}{10}= 1[/tex]
and
[tex]\frac{(\sqrt{3})^2}{30}+ \frac{3^2}{10}= 1[/tex] ?
And don't forget that you were told there were two possible answers. What is the other answer?