观察下列各式: (x-1)(x+1)=x2-1;

(x-1)(x2+x+1)=x3-1;

(x-1)(x3+x2+x+1)=x4-1;

… … …

(1)根据规律填空 (x-1)(xn+xn-1+…+x+1)=__ __________.

(2)根据规律计算 2100+299+298+297+…+22+2 +1=       .

(1) xn+1-1         (2) 2101-1

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