怎样计算(a-1)/(a^2-4)-1/(a+2)+(a+1)/(a^2-4a+4)?

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怎样计算(a-1)/(a^2-4)-1/(a+2)+(a+1)/(a^2-4a+4)?

怎样计算(a-1)/(a^2-4)-1/(a+2)+(a+1)/(a^2-4a+4)?
怎样计算(a-1)/(a^2-4)-1/(a+2)+(a+1)/(a^2-4a+4)?

怎样计算(a-1)/(a^2-4)-1/(a+2)+(a+1)/(a^2-4a+4)?

原式=(a-1)/(a+2)(a-2)-1/(a+2)+(a+1)/(a-2)²
=[(a-1)(a-2)-(a-2)²+(a+1)(a-1)]/(a+2)(a-2)²
=(a²-3a+2-a²+4a-4+a²-1)/(a+2)(a-2)²
=(a²+a-3)/(a+2)(a-2)²