Question 966295
{{{r=10/(2-x/R)}}}
{{{r(2-x/R)=10}}}
{{{2r-x=10}}}
{{{2r=10+x}}}
{{{4r^2=(10+x)^2}}}
{{{4(x^2+y^2)=x^2+20x+100}}}
{{{4x^2+4y^2-x^2-20x-100=0}}}
{{{3x^2-20x+4y^2=100}}}
{{{3(x^2-(20/3)x+(10/3)^2)+4y^2=100+3(10/3)^2}}}
{{{3(x-10/3)^2+4y^2=100+3(100/9)}}}
{{{3(x-10/3)^2+4y^2=900/9+300/9}}}
{{{3(x-10/3)^2+4y^2=1200/9}}}
{{{3(x-10/3)^2+4y^2=400/3}}}
{{{3(x-10/3)^2+4y^2=400/3}}}
{{{ (9(x-10/3)^2)/400+(3y^2)/100=1 }}}
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  *[illustration dd5.JPG].