10 x ( 9+ 1 )

10 x 10=100

99

220

cầu xin tích mik mik thề sẽ tích lại

10 x ( 9+ 1 )

10 x 10=100

99

220

cầu xin tích mik mik thề sẽ tích lại

9.10+10.1=10.(9+1)=10.10=100

11.9=99

22.10=220

Vậy thì bạn ...k mik trước đi đã 

\(=\dfrac{3}{9}\cdot\dfrac{9}{11}\cdot\dfrac{22}{25}\cdot\dfrac{5}{7}\cdot\dfrac{7}{10}=\dfrac{3}{11}\cdot\dfrac{22}{25}\cdot\dfrac{5}{10}=3\cdot2\cdot\dfrac{1}{2}\cdot\dfrac{1}{5}=\dfrac{3}{5}\)

\(=\dfrac{3x4x9x11x2x5x7}{4x9x11x5x5x10}=\dfrac{3x2x7}{10}=\dfrac{42}{10}=\dfrac{21}{5}\)

=3/9⋅9/11⋅22/25⋅5/7⋅7/10=3/11⋅22/25⋅5/10=3⋅2⋅1/2⋅1/5=3/5

\(\dfrac{3}{8}+\dfrac{-11}{8}=1\)

\(\dfrac{22}{9}+\dfrac{10}{18}=3\)

1<x<3

=>x=2

Bài 3:

\(a,\dfrac{x-1}{10}+\dfrac{x-1}{11}=\dfrac{x-1}{12}+\dfrac{x-1}{13}\)

\(\Rightarrow\dfrac{x-1}{10}+\dfrac{x-1}{11}-\dfrac{x-1}{12}-\dfrac{x-1}{13}=0\)

\(\Rightarrow\left(x-1\right)\left(\dfrac{1}{10}+\dfrac{1}{11}-\dfrac{1}{12}-\dfrac{1}{13}\right)=0\)

Mà \(\dfrac{1}{10}+\dfrac{1}{11}-\dfrac{1}{12}-\dfrac{1}{13}\ne0\)

\(\Rightarrow x-1=0\Rightarrow x=1\)

Vậy x = 1

b, \(\dfrac{x-2000}{10}+\dfrac{x-1999}{9}=\dfrac{x-1998}{8}+\dfrac{x-1997}{7}\)

\(\Rightarrow\dfrac{x-2000}{10}+1+\dfrac{x-1999}{9}+1=\dfrac{x-1998}{8}+\dfrac{x-1997}{7}+1\)

\(\Rightarrow\dfrac{x-1990}{10}+\dfrac{x-1990}{9}-\dfrac{x-1990}{8}-\dfrac{x-1990}{7}=0\)

\(\Rightarrow\left(x-1990\right)\left(\dfrac{1}{10}+\dfrac{1}{9}-\dfrac{1}{8}-\dfrac{1}{7}\right)=0\)

Mà \(\dfrac{1}{10}+\dfrac{1}{9}-\dfrac{1}{8}-\dfrac{1}{7}\ne0\)

\(\Rightarrow x-1990=0\Rightarrow x=1990\)

Bài 2:

a: 2/6x5/3=10/18=5/9

b: 11/9x5/10=55/90=11/18

c: 3/9x6/8=1/3x3/4=1/4

d: 4/9x12/16=48/144=1/3

e: 25/15x6/7=5/3x6/7=30/21=10/7

f: 6/10x15/20=90/200=9/20

Bài 1

4/5 x 6/7= 24/35

2/9 x 1/2= 2/18= 1/9

1/2 x 8/3= 8/6= 4/3

7/9 x 6/5= 42/45= 14/15

8/7 x 5/9= 40/63

10/11 x 22/15= 220/165= 4/3

Bài 2

2/6 x 5/3= 1/3 x 5/3=5/9

11/9 x 5/10= 11/9 x 1/2= 11/18

3/9 x 6/8= 1/3 x 3/4 =3/12= 1/4

4/9 x 12/16= 4/9 x 3/4= 12/36= 1/3

25/15 x 6/7= 5/3 x 6/7= 30/21= 10/7

6/10 x 15/20= 3/5 x 3/4= 9/20

bài 1

4/5 x 6/7 = 24/35

2/9 x 1/2 = 1/9

1/2 x 8/3 = 4/3

7/9 x 6/5 = 14/15

8/7 x 5/9 = 14/15

8/7 x 5/9 = 40/63

10/11 x 22/15 = 4/3

\(a,\frac{x-22}{8}+\frac{x-21}{9}+\frac{x-20}{10}+\frac{x-19}{11}\)

\(a,\frac{x-22}{8}+\frac{x-21}{9}+\frac{x-20}{10}+\frac{x-19}{11}=4\)

\(\Leftrightarrow\frac{x-22}{8}-1+\frac{x-21}{9}-1+\frac{x-20}{10}-1+\frac{x-19}{11}-1=0\)

\(\Leftrightarrow\frac{x-30}{8}+\frac{x-30}{9}+\frac{x-30}{10}+\frac{x-30}{11}=0\)

\(\Leftrightarrow\left(x-30\right)\left(\frac{1}{8}+\frac{1}{9}+\frac{1}{10}+\frac{1}{11}\right)=0\)

\(\Leftrightarrow\left(x-30\right)=0\)

\(\Leftrightarrow x=30\)

\(b,\frac{-x+12}{7}+\frac{-x+13}{6}=\frac{-x+15}{4}+\frac{-x+16}{3}\)

\(\Leftrightarrow\frac{-x+12}{7}+1+\frac{-x+13}{6}+1=\frac{-x+15}{4}+1+\frac{-x+16}{3}+1\)

\(\Leftrightarrow\frac{19-x}{7}+\frac{19-x}{6}-\frac{19-x}{4}-\frac{19-x}{3}=0\)

\(\Leftrightarrow\left(19-x\right)\left(\frac{1}{7}+\frac{1}{6}-\frac{1}{4}-\frac{1}{3}\right)=0\)

\(\Leftrightarrow19-x=0\)

\(\Leftrightarrow x=19\)

10 x 10 x 9 x 22 

= 20 x 9 x 22

= 270 x 22

= 19800

19800

=19800 NHA BN