(a²-4)分之4+(a+2)分之2-(a-2)分之1=[(a+2)(a-2)]分之4+[(a+2)(a-2)]分之[2(a-2)]-[(a+2)(a-2)]分之(a+2)=[(a+2)(a-2)]分之[4+2(a-2)-(a-2)]=[(a+2)(a-2)]分之(a+2)=(a-2)分之1