19.已知实数aaa,bbb,xxx,yyy满足x2a2−y2b2=1\frac{x^2}{a^2}-\frac{y^2}{b^2}=1a2x2−b2y2=1. (1)试比较a2−b2a^{2}-b^{2}a2−b2和(x−y)2(x-y)^{2}(x−y)2的大小; (2)利用(1)的结论,比较3m−5−m−2\sqrt{3m-5}-\sqrt{m-2}3m−5−m−2与63\frac{\sqrt{6}}{3}36的大小.