=[(1-3)+(5-7)+(9-11)+...(45-47)+49]+[(51-53)+(55-57)+.....(95-97)+99)
= [(-2)x12+49]+[(-2x12)+99]
=(-24+49)+(-24+99)
= 25+75
=100
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Các câu hỏi tương tự
1+3-5+7-9+11-......91-93+95-97+99
99-97+95-93+91-89+...+9-7+5-3+1
Tính nhanh:
a) (1374.57+687.86).(26.14+74.14)
b)99-97+95-93+91-89+...+7-5+3-1
c)5+6-7-8+9+10-11-12+13+...-299-300+301+302
99 - 97 + 95 - 93 + 91 - 89 +........+7 - 5 + 3 - 1
99-97 +95-93+91-89+...+7-5+3-1 = ?
99-97+95-93+91-89+.....+7-5+3-1=?
99-97+95-93+91-89+...+7-5+3-1
A=99-97+95-93+91-89+...+7-5+3-1
G = 99 - 97 + 95 - 93 + 91 - 89 + ........ + 7 - 5 + 3 - 1 = ?
G = 99 - 97 + 95 - 93 + 91 - 89 + ........... + 7 - 5 +3 - 1