Question 838333
Transform your equation to 
{{{x^2/a^2+y^2/b^2=1}}}
Then
{{{c^2=a^2-b^2}}}
.
.

{{{2x^2+7y^2=14}}}
{{{x^2/7+y^2/2=1}}}
{{{a=sqrt(7)}}}
{{{b=sqrt(2)}}}
{{{c^2=7-2}}}
{{{c^2=5}}}
{{{c=sqrt(5)}}}
{{{e=c/a=sqrt(5)/sqrt(7)=sqrt(5/7)}}}