[(a^3-a^2-2a-8)/(2根号下1+a^2)]^2=[(a^2+2a)^2+(a^2+2a+8)^2]/4 怎么化简成一般

[(a^3-a^2-2a-8)/(2根号下1+a^2)]^2=[(a^2+2a)^2+(a^2+2a+8)^2]/4
(a^3-a^2-2a-8)^2/(4+4a^2)=[(a^2+2a)^2+(a^2+2a+8)^2]/4
(a^3-a^2-2a-8)^2=(a^2+1)*[(a^2+2a)^2+(a^2+2a+8)^2]
[a^3-(a^2+2a+8)]^2=(a^2+1)*[(a^2+2a)^2+(a^2+2a+8)^2]
a^6-2a^3*(a^2+2a+8)+(a^2+2a+8)^2=(a^2+1)(a^2+2a+8)^2+(a^2+1)(a^2+2a)^2
a^6-2a^3*(a^2+2a+8)=a^2(a^2+2a+8)^2+a^2(a^2+1)(a+2)^2
a^6-3a^3*(a^2+2a+8)-a^2(a^2+1)(a+2)^2=0
a^2(a^4-3a^3-6a^2-24a-a^4-4a^3-5a^2-4a-4)=0
a^2(7a^3+11a^2+28a+4)=0
a=0或7a^3+11a^2+28a+4=0
7a^3+11a^2+28a+4=0
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