3- 32/ 35

= 3/1- 32/35

= 105/35- 32/35

= 73/35

ko trl cho người ta thì thôi đi,mắc j phải chửi

1 x 2 = 2 

5 x 6 = 30 

2 x 3 = 6 

6 x 7 = 42 

3 x 4 = 12 

7 x 8 = 56 

4 x 5 = 20 

8 x 9 = 72 

HT

TL

1x2=2           2x3=6               3x4=12                     4x5=20

5x6=30             6x7=42                    7x8=56                      8x9=72

nha

HT

=1/6-1/7+1/7-1/8+1/8-1/9+...+1/10-1/11

=1/6-1/11=5/66

   \(\dfrac{1}{5\times6}+\dfrac{1}{6\times7}+\dfrac{1}{7\times8}+\dfrac{1}{8\times9}+\dfrac{1}{9\times10}\)

= \(\dfrac{1}{5}-\dfrac{1}{6}\times\dfrac{1}{6}-\dfrac{1}{7}\times\dfrac{1}{7}-\dfrac{1}{8}\times\dfrac{1}{8}-\dfrac{1}{9}\times\dfrac{1}{9}-\dfrac{1}{10}\)

= \(\dfrac{1}{5}-\dfrac{1}{10}\)  

= \(\dfrac{1}{10}\)

Bài tập cuối tuần 10

`1/[4xx5]+1/[5xx6]+1/[6xx7]+1/[7xx8]+1/[8xx9]+1/[9xx10]`

`=1/4-1/5+1/5-1/6+1/6-1/7+1/7-1/8+1/8-1/9+1/9-1/10`

`=1/4-1/10`

`=10/40-4/40=6/40=3/20`

\(A=\dfrac{1}{2}-\dfrac{1}{3}+\dfrac{1}{3}-\dfrac{1}{4}+...+\dfrac{1}{7}-\dfrac{1}{8}=\dfrac{1}{2}-\dfrac{1}{8}=\dfrac{3}{8}\)

5/6+1/6=1

3-32/35=73/35

5/6+3/8:9/4= 5/6 + 1/6= 6/6= 1

3-4/7x8/5= 3- 32/35= 3/1-32/35= 73/35

\(=\dfrac{720}{7}\cdot8-9+10\cdot15\)

=5760/7+141

=6747/7