题目：
计算下列各题：
（1）（a-1）（a+1）=__________
（a-1）（a2+a+1）=__________
（a-1）（a3+a2+a+1）=_________
……
根据前面各式的规律，请你写出：
（a-1）（an+an-1+an-2+…+a3+a2+a+1）=__________；
（2）利用（1）的结论，计算：
299+298+297+…+22+2+1
答案：
解：（1）
，
，
，
；
（2）原式
…+
。
计算下列各题： （1）（a-1）（a+1）=__________ （a-1）（
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题型：解答题
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