a=根号5-1/2求a的5次方+a的4次方-2a的3次方-a的2次方-a+2/a的3次方-a的值
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a = (√5-1)/2 ,
2a = √5-1 ,
2a+1 = √5 ,
(2a+1)² = (√5)² ,
4a²+4a+1 = 5 ,
4a²+4a-4 = 0 ,
a²+a-1 = 0 ,
(a^5+a^4-2a^3-a^2-a+2)/(a^3-a)
= [a^3(a²+a-1)-a(a²+a-1)-2(a-1)]/[a(a+1)(a-1)]
= -2(a-1)/[(a²+a)(a-1)]
= -2/[(a²+a-1)+1]
= -2/1
= -2
2a = √5-1 ,
2a+1 = √5 ,
(2a+1)² = (√5)² ,
4a²+4a+1 = 5 ,
4a²+4a-4 = 0 ,
a²+a-1 = 0 ,
(a^5+a^4-2a^3-a^2-a+2)/(a^3-a)
= [a^3(a²+a-1)-a(a²+a-1)-2(a-1)]/[a(a+1)(a-1)]
= -2(a-1)/[(a²+a)(a-1)]
= -2/[(a²+a-1)+1]
= -2/1
= -2
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