more simple solution (sqr(x)+sqr(x-9))*(sqr(x)-sqr(x-9))/(sqr(x)-sqr(x-9))=9 (x-x+9)/(sqr(x)-sqr(x-9))=9 9/(sqr(x)-sqr(x-9))=9 1/(sqr(x)-sqr(x-9))=1 sqr(x)-sqr(x-9)=1 and we have now sqr(x)+sqr(x-9)=9 sqr(x)-sqr(x-9)=1 _________________ 2*sqr(x)=10 sqr(x)=5 and finally x=25
