化简：①.(x²-y²)÷(√x+√y)= ②.a√[-（a+1）/a²]=化简：①.(x²-y²)÷(√x+√y)= ②.a√[-（a+1）/a²]= ③.若0

化简：①.(x²-y²)÷(√x+√y)= ②.a√[-（a+1）/a²]=化简：①.(x²-y²)÷(√x+√y)= ②.a√[-（a+1）/a²]= ③.若0
化简：①.(x²-y²)÷(√x+√y)= ②.a√[-（a+1）/a²]=
化简：①.(x²-y²)÷(√x+√y)= ②.a√[-（a+1）/a²]= ③.若0

化简：①.(x²-y²)÷(√x+√y)= ②.a√[-（a+1）/a²]=化简：①.(x²-y²)÷(√x+√y)= ②.a√[-（a+1）/a²]= ③.若0
①.(x²-y²)÷(√x+√y)
= (x+y)(x-y)÷(√x+√y)
=(x+y)(√x+√y)(√x-√y)÷(√x+√y)
=(x+y)(√x-√y)
②.a√[-（a+1）/a²]=
因为根号里面要大于等于0,所以：
-（a+1）>0
a+1

1. =(x+y)(x-y)/(√x+√y)

   =(x+y)(√x+√y)(√x-√y)/(√x+√y)

   =(x+y)(√x-√y)

2. =-(a/a)√(-a-1)

   =-√(-a-1)

3. ==√[a^2+1/a^2+2-4]
   =√[a^2+1/a^2-2]
   =√(a-1/a)^2

   =(1-a)/a

①原式=（x²-y²)(√x-√y)/(x-y)
=(x+y)(√x-√y)
=x√x-x√y+y√x-y√y
②∵-（a+1)/a²≥0
∴a≤-1<0
∴原式=a/|a|·√(-a-1)=a/(-a)·√(-a-1)=-√(-a-1)
③原式=√（a-1/a)²=|a-1/a|
...

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①原式=（x²-y²)(√x-√y)/(x-y)
=(x+y)(√x-√y)
=x√x-x√y+y√x-y√y
②∵-（a+1)/a²≥0
∴a≤-1<0
∴原式=a/|a|·√(-a-1)=a/(-a)·√(-a-1)=-√(-a-1)
③原式=√（a-1/a)²=|a-1/a|
当a<-1或者0当-1≤a<0或者a≥1时，原式=a-1/a

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