已知a + 1
已知a + 1/a = 5 求: a4/a2 + a2 + 1的值
此题有误,应为:已知a + 1/a = 5 求: a2/a4+ a2 + 1的值 解;a + 1/a = 5 (a + 1/a )^2=25 a^2/a^4 + a^2 +2=25 a^2/a^4+ a^2 =23 a^2/a^4 + a^2 +1 =24
a4/a2 + a2 + 1 看不懂 分子,分母各是什么,没有括号,看不明白
a + 1/a = 5 (*a) a^2 + 1 = 5a a^2 = 5a-1 a^4/a^2 + a^2 +1 = 0 a^(4-2) + a^2 + 1 = 0 2 a^2 + 1 = 0 , (a^2 = 5a-1) 2(5a - 1) + 1 = 0 10a - 2 + 1 = 0 10a - 1 = 0 10a = 1 a = 1/10
答:a^2=a+1 两边平方 a^4=a^2+2a+1=(a+1)+2a+1)=3a+2 a^5=a^4*a=3a^2+2a=3(a+1)+2a=5a+1 a^5-...详情>>
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