1. Tính a) $\frac{3}{4}$-$\frac{3}{2}$+ $\frac{1}{2}$/ $\frac{5}{12}$ b) $\frac{1}{2.3}$+ $\frac{1}{3.4}$+ $\frac{1}{4.5}$+…+ $\frac{1}{99.100}

0 bình luận về “1. Tính a) $\frac{3}{4}$-$\frac{3}{2}$+ $\frac{1}{2}$/ $\frac{5}{12}$ b) $\frac{1}{2.3}$+ $\frac{1}{3.4}$+ $\frac{1}{4.5}$+…+ $\frac{1}{99.100}”

1. a, $\frac{3}4-\frac{3}2+\frac{1}2÷\frac{5}{12}$

   $=\frac{3-6}4+\frac{1}2·\frac{12}5$

   $=-\frac{3}4+\frac{6}5$

   $=\frac{-15+24}{20}=\frac{9}{20}$

   b, $\frac{1}{2.3}+\frac{1}{3.4}+\frac{1}{4.5}+…+\frac{1}{99.100}$

   $=\frac{1}2-\frac{1}3+\frac{1}3-\frac{1}4+\frac{1}4-\frac{1}5+…+\frac{1}{99}-\frac{1}{100}$

   $=\frac{1}2-\frac{1}{100}=\frac{50-1}{100}=\frac{49}{100}$

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2. Đáp án:+Giải thích các bước giải:

   `a)`
   `(3/4-3/2+1/2)/(5/12`
   `=(3/4-6/4+2/4)/(5/12)`
   `=(-1/4)/(5/12)`
   `=-1/4:5/12`
   `=-1/4 . 12/5`
   `=-3/5`
   `b)`
   `1/(2.3) +1/(3.4)+1/(4.5)+…+1/(99.100)`
   `=1/2-1/3+1/3-1/4+1/4-1/5+…+1/99-1/100`
   `=1/2-1/100`
   `=50/100-1/100`
   `=49/100`

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