(51+52.+99+100)-(1+2+3+.+49+50)怎么做
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(51+52.+99+100)-(1+2+3+.+49+50)怎么做
(51+52.+99+100)-(1+2+3+.+49+50)怎么做
(51+52.+99+100)-(1+2+3+.+49+50)怎么做
用前一个数加后一个数也就和、
(51+52.+99+100)-(1+2+3+.+49+50)
=(50+1+50+2+50+3...+50+50)-(1+2+3+...+49+50)
=50*50+1+2+3+...+50-(1+2+3+...+49+50)
=2500
(51+52.......+99+100)-(1+2+3+......+49+50)
=(51-1)+(52-2)+......+(99-49)+(100-50)
=50+50+.....+50 - - - - - - -- -- 共50个50
=2500
(51+52.......+99+100)-(1+2+3+......+49+50)
=(50+1+50+2+50+3...+50+50)-(1+2+3+...+49+50)
=50*50+1+2+3+...+50-(1+2+3+...+49+50)
=2500
(51+52.......+99+100)-(1+2+3+......+49+50)
=(50+1+50+2+50+3...+50+50)-(1+2+3+...+49+50)
=50*50+1+2+3+...+50-(1+2+3+...+49+50)
=2500
(51+52.......+99+100)-(1+2+3+......+49+50)
=(50+1+50+2+50+3...+50+50)-(1+2+3+...+49+50)
=2500