99...9*99...9+199...9 1998个9 1998个9 1998个9

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99...9*99...9+199...91998个91998个91998个999...9*99...9+199...91998个91998个91998个999...9*99...9+199...91

99...9*99...9+199...9 1998个9 1998个9 1998个9
99...9*99...9+199...9 1998个9 1998个9 1998个9

99...9*99...9+199...9 1998个9 1998个9 1998个9
令a=1998个9
则原式=a²+2a+1
=(a+1)²
=100……0,(3996个0)