Question 920348

{{{ax+x^2=y^2-ay}}}

{{{ax+ay=y^2-x^2}}}

{{{a(x+y)=y^2-x^2}}}

{{{a=(y^2-x^2)/(x+y)}}}

{{{a=((y-x)(y+x))/(x+y)}}}

{{{a=((y-x)cross((y+x)))/cross((x+y))}}}

{{{a=y-x}}}