(探究创新题)计算3620-1-2-3...-76-77-78-79

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(探究创新题)计算3620-1-2-3...-76-77-78-79

(探究创新题)计算3620-1-2-3...-76-77-78-79
(探究创新题)计算3620-1-2-3...-76-77-78-79

(探究创新题)计算3620-1-2-3...-76-77-78-79
3620-1-2-3...-76-77-78-79
=3620-(1+2+3...+76+77+78+79)
=3620-〔(1+79)+(2+78)+(3+77)+...+(39+41)+40〕
=3620-(39*80+40)
=460

3620-(1+2+3+……+76+77+78+79)=3620-(1+79)*79/2=3620-3160=460

3620-[(1+79)+(2+78)+…+(39+41)+40]=3620-[80*39+40]=3620-[3120+40]=3620-3160=460

4000-1-2-3...-77-78