先化简,在求值；a/a+1-a平方-3a/a+3除以a平方-6a+9/a平方-9,其中a=-2

a/a+1-a平方-3a/a+3除以a平方-6a+9/a平方-9,其中a=-2
=a/(a+1)-a(a+3)/(a+3)÷(a-3)²/(a-3)(a+3)
=a/(a+1)-a÷(a-3)/(a+3)
=a/(a+1)-a(a+3)/(a-3)
=(a²-3a-a³-4a²-3a)/(a+1)(a-3)
=(-a³-3a²-6a)/(a+1)(a-3)
=(-8-12+12)/(-2+1)(-2-3)
=-8/5
(-8/5)²=64/25