先化简,再求值[(a^3+2a^2+4a)/(a-2)(a^2+2a+4)]-10/(a^2+a-6)除以[1- 21/(a^2-_数学解答

先化简,再求值[(a^3+2a^2+4a)/(a-2)(a^2+2a+4)]-10/(a^2+a-6)除以[1- 21/(a^2-4)]*(a+3)/(a-2),其中a=1/2

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解答

[(a^3+2a^2+4a)/(a-2)(a^2+2a+4)]-10/(a^2+a-6)除以[1- 21/(a^2-4)]*(a+3)/(a-2)=[a(a^2+2a+4)/(a-2)(a^2+2a+4)]-10/(a^2+a-6)*[(a^2-4)/(a^2-4)-21]*(a+3)/(a-2)=a/(a-2)-10/(a+3)(a-2)*[(a-2)(a+2)/(a^2-4)-21]*(a...