$\displaystyle x^2/2+y^2/1=1$

I'm not sure how to get $\displaystyle a^2$ or $\displaystyle b^2$ in this problem. My book shows $\displaystyle a^2$ as 2root2 and $\displaystyle b^2$ as 2 but gives no explanation as to how they got those answers. I guess my problem is really that I'm not sure how to get the major and minor axis when they aren't numbers that can easily be squared.