√(x+1)+√(y+1)=3,xy-x-y+15=0令√(x+1)=m √(y+1)=n则x=m^2-1 y=n^2-1m+n=3xy-x-y+15=(x-1)(y-1)+14=(m^2-1)(n^2-1)+14=0m^2n^2-2m^2-2n^2+18=0但是2(m^2+n^2)=2[(m+n)^2-2mn]=18-4mn即(mn)^2-18+4mn+18=0所以mn=0...