Đáp án:

`A = 1/5`

`B = 1/100`

`C = 1/33`

Giải thích các bước giải:

 Bài `1:`

`a)` `A = (1 - 1/2) xx (1 - 1/3) xx (1 - 1/4) xx (1 - 1/5)`

    `A = 1/2 xx 2/3 xx 3/4 xx 4/5`

    `A =` $\dfrac{1 \times 2 \times 3 \times 4}{2 \times 3 \times 4 \times 5}$ 

    `A = 1/5`

`b)` Sửa lại đề:

    `B = (1 - 3/4) xx (1 - 3/7) xx (1- 3/10) xx (1 - 3/13) xx ... xx (1 - 3/100)`

    `B = 1/4 xx 4/7 xx 7/10 xx 10/13 xx ... xx 97/100`

    `B =` $\dfrac{1 \times 4 \times 7 \times 10 \times ... \times 97}{4 \times 7 \times 10 \times 13 \times ... \times 100}$ 

    `B = 1/100`

`c)` `C = (1 - 2/5) xx (1 - 2/7) xx (1 - 2/9) xx (1 - 2/11) xx ... xx (1 - 2/99)`

   `C = 3/5 xx 5/7 xx 7/9 xx 9/11 xx ... xx 97/99`

   `C =` $\dfrac{3 \times 5 \times 7 \times 9 \times ... \times 97}{5 \times 7 \times 9 \times 11 \times ... \times 99}$ 

   `C = 3/99`

   `C = 1/33`

CHÚC BẠN HỌC TỐT!

a) A = (1 - $\frac{1}{2}$) × (1 - $\frac{1}{3}$) × (1 - $\frac{1}{4}$) × $\frac{1}{5}$)

    A = $\frac{1}{2}$ × $\frac{2}{3}$ ×$\frac{3}{4}$ × $\frac{4}{5}$ 

    A = $\frac{1 × 2 × 3 × 4}{2 × 3 × 4 × 5}$ 

    A = $\frac{1}{5}$ 

b) B = (1 - $\frac{3}{4}$) × (1 - $\frac{3}{7}$) × (1 - $\frac{3}{10}$) × ... × (1 - $\frac{3}{100}$)

    B = $\frac{1}{4}$ × $\frac{4}{7}$ × $\frac{7}{10}$ × ... × $\frac{97}{100}$ 

    B = $\frac{1 × 4 × 7 × ... × 97}{4 × 7 × 10 × ... × 100}$ 

    B = $\frac{1}{100}$ 

c) C = (1 - $\frac{2}{5}$) × (1 - $\frac{2}{7}$) × (1 - $\frac{2}{9}$) × ... × (1 - $\frac{2}{99}$)

    C = $\frac{3}{5}$ × $\frac{5}{7}$ × $\frac{7}{9}$ × ... × $\frac{97}{99}$ 

    C = $\frac{3 × 5 × 7 × ... × 97}{5 × 7 × 9 × ... 99}$ 

    C = $\frac{3}{99}$ 

    C = $\frac{1}{33}$ 

                    Chúc bạn học tốt!

                    Xin hay nhất!