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原式=(1+10+100+…+100000000+2+20+200+…20000000+…+8+80+9)/4 =[(1+2+3+4+…+8+9)+(10+20+30+…+80)+…+100000000]/4 =(45+360+2800+21000+150000+1000000+6000000+30000000+100000000)/4 =45/4+3…
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