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计算.(1)1+416+7112+10120+13130+16142+19156+22172

2022-08-14 02:50:53 问答库 阅读 200 次

问题详情

计算.
(1)1+41

6

+71

12

+101

20

+131

30

+161

42

+191

56

+221

72

+251

90


(2)(17

11

+18

21

+19

31

+20

41

)×(18

21

+19

31

+20

41

+21

51

)-(17

11

+18

21

+19

31

+20

41

+21

51

)×(18

21

+19

31

+20

41

).

参考答案

(1)1+416+7112+10120+13130+16142+19156+22172+25190,
=(1+4+7+10+13+16+19+22+25)+(16+112+120+130+142+156+172+190),
=117+(12-13+13-14+14-15+15-16+16-17+17-18+18-19+19-110),
=117+(12-110),
=117+25,
=11725;

(2)设1711+1821+1931+2041=a,1821+1931+2041=b,则a-b=1711+1821+1931+2041-(1821+1931+2041)=1711,那么:
(1711+1821+1931+2041)×(1821+1931+2041+2151)-(1711+1821+1931+2041+2151)×(1821+1931+2041),
=a×(b+2151)-(a+2151)×b,
=ab+2151a-ab-2151b,
=2151×(a-b),
=2151×1711,
=711.

考点: