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4/7x = 9/8 - 0,125

4/7x = 9/8 - 1/8

4/7x = 1

      x = 1 : 4/7

      x = 7/4

=^_^=

k mình nha

\(\frac{4}{7}x=\frac{9}{8}-0,125\)

\(\frac{4}{7}x=\frac{9}{8}-\frac{1}{8}\)

\(\frac{4}{7}x=\frac{8}{8}\)

\(\frac{4}{7}x=1\)

\(x=1:\frac{4}{7}\)

\(x=1\times\frac{7}{4}\)

\(x=\frac{7}{4}\)

Ta thấy

1.3.5.....19 = 1.2.3.4.5.6.....19.20/2.4.6.....20

= 1.2.3.4.5.6.....19.20/1.2.2.2.3.2.....10.2

= 1.2.3.4.5.6.....19.20/(1.2.3.....10).(2.2.2.....2) 

= (1.2.3.4.5.6.....10).(11.12.13.....19.10)/(1.2.3.....10).(2.2.2.....2)

= 11.12.13.....19.20/2.2.2.....2

= 11/2 . 12/2 . 13/2 . ... . 19/2 . 20/2

=> Đpcm

2/3+x=-45%

2/3+x=-9/20

x=-9/20-2/3

x=-67/60

Vậy x= -67/60

2/3 + x = -45%

2/3 + x = -9/20

           x = -9/20 - 2/3

           x = -67/60

=^_^=

k mình nha

(-150) x 2/3 = -100

2/3 của x là (-150)

Suy ra: x = (-150) : 2/3

Vậy x = -100

=^_^=

k mình nha

\(A=\frac{1}{3.41}+\frac{1}{4.42}+...+\frac{1}{33.71}\)

\(\Leftrightarrow A=\frac{1}{38}\left(\frac{1}{3}-\frac{1}{41}+\frac{1}{4}-\frac{1}{42}+...+\frac{1}{33}-\frac{1}{71}\right)\)

\(B=\frac{1}{3.34}+\frac{1}{4.35}+...+\frac{1}{46.71}\)

\(\Leftrightarrow B=\frac{1}{31}\left(\frac{1}{3}-\frac{1}{34}+\frac{1}{4}-\frac{1}{35}+...+\frac{1}{46}-\frac{1}{71}\right)\)

​\(\Leftrightarrow B=\frac{1}{31}\left(\frac{1}{3}-\frac{1}{41}+\frac{1}{4}-\frac{1}{42}+...+\frac{1}{33}-\frac{1}{71}\right)\)​

\(\Leftrightarrow\frac{A}{B}=\frac{31}{38}\)