(1)
2a/(a²-4)+1/(2-a)
=2a/(a²-4)-(a+2)/(a²-4)
=(a-2)/(a²-4)
=1/(a+2)
=1/(5/2)
=2/5
(2)
(a+2b)/(a+b)+2b²/(a²-b²)
=(a+2b)(a-b)/(a²-b²)+2b²/(a²-b²)
=a/(a-b)
=(-2)/(-2-1/3)
=6/7
(3)
(x²-1)/(x²+2x+1)-(x+1)/(x-1)
=(x-1)/(x+1)-(x+1)/(x-1)
=[(x-1)²-(x+1)²]/[(x+1)(x-1)]
=-4x/[(x+1)(x-1)]
=0(x=0)
=-8/3(x=-2、2)