1.2+5*(1+2+3...+99)
=2+5*[(1+99)*99]/2
=2+5*(9900/2)
=2+5*4950
=24750+2
=24752
2.7*100+6*(1+2+3..+100)
=700+6*5050
=31000
是"簡(jiǎn)單數(shù)列求和"
是"簡(jiǎn)單數(shù)列求和"
(1) 2+5+10+15+…+5 * 99
(2) (7+6) + (7+6 * 2) + … + (7+6 * 99) + (7+6 * 100)
(1) 2+5+10+15+…+5 * 99
(2) (7+6) + (7+6 * 2) + … + (7+6 * 99) + (7+6 * 100)
數(shù)學(xué)人氣：912 ℃時(shí)間：2020-06-02 21:03:33
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