(1)
(x²-y²)/(x²-2xy+y²)
=(x-y)(x+y)/(x-y)²
=(x+y)/(x-y)
x²＋y²－2x－6y＋10＝0
x²-2x+1+y²-6y+9=0
(x-1)²+(y-3)²=0
非负式
所以x=1,y=3
原式
=(1+3)/(1-3)
=-2
(2)
[﹙a＋1﹚﹙a＋3﹚﹙2a－a²﹚]/[﹙a³＋a²﹚﹙a－2﹚﹙a＋3﹚]
=[(a+1)(a+3)a(2-a)]/[a²(a+1)(a-2)(a+3)]
=-1/a
a=-3/4
原式
=4/3
即3分之4