作业帮1.已知,a=1/√2+1,求a³+a²-3a-1的值2.化简（1/√3+1）+（1/√5+√3）+（1/√7+√5）+…+[1/(根号下2n+1)+根号下2n-1]
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![1.已知,a=1/√2+1,求a³+a²-3a-1的值2.化简（1/√3+1）+（1/√5+√3）+（1/√7+√5）+…+[1/(根号下2n+1)+根号下2n-1]](/uploads/image/z/2589676-52-6.jpg?t=1.%E5%B7%B2%E7%9F%A5%2Ca%3D1%2F%E2%88%9A2%2B1%2C%E6%B1%82a%26%23179%3B%2Ba%26%23178%3B-3a-1%E7%9A%84%E5%80%BC2.%E5%8C%96%E7%AE%80%EF%BC%881%2F%E2%88%9A3%2B1%EF%BC%89%2B%EF%BC%881%2F%E2%88%9A5%2B%E2%88%9A3%EF%BC%89%2B%EF%BC%881%2F%E2%88%9A7%2B%E2%88%9A5%EF%BC%89%2B%E2%80%A6%2B%5B1%2F%28%E6%A0%B9%E5%8F%B7%E4%B8%8B2n%2B1%29%2B%E6%A0%B9%E5%8F%B7%E4%B8%8B2n-1%5D)
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1.已知,a=1/√2+1,求a³+a²-3a-1的值2.化简（1/√3+1）+（1/√5+√3）+（1/√7+√5）+…+[1/(根号下2n+1)+根号下2n-1]
1.已知,a=1/√2+1,求a³+a²-3a-1的值
2.化简（1/√3+1）+（1/√5+√3）+（1/√7+√5）+…+[1/(根号下2n+1)+根号下2n-1]
1.已知,a=1/√2+1,求a³+a²-3a-1的值2.化简（1/√3+1）+（1/√5+√3）+（1/√7+√5）+…+[1/(根号下2n+1)+根号下2n-1]
1.a = v2 -1,直接算即得 -2
2.1/(根号下2n+1)+根号下2n-1] = 1/2 *((根号下2n+1)-根号下2n-1)
累加,中间抵消,得 1/2*((根号下2n+1)-1)