Tìm tổng

N

nhokpooh98yb

a


a) 100 + (98-97)+(96-95)+(94-93)+....+(52-51)+...… = 100+1+1+...+1 = 100+49=149
b) 100 - 99 + 98 - 97 + 96 - 95+...+ 6 - 5 + 4 - 3 + 2 - 1
=(100-99+98-97)+(96-95+94-93)+......+(4-3+2-1)
=2+2+2+2.....+2(25 số hạng)
=2.25
=50
 
P

phamhienhanh21

b) 100 - 99 + 98 - 97 + 96 - 95 + ... + 2 - 1
=[TEX] \begin{matrix} \underbrace{ (100-99)+(98-97)+(96-95)+\cdots+(2-1) } \\ 50 \end{matrix}[/TEX]
=[TEX]\begin{matrix} \underbrace{1+1+1+\cdots+1 } \\ 50 \end{matrix}[/TEX]
=1x50
=50
 
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