\(x-\dfrac{1}{3}=\dfrac{2}{3}.\dfrac{9}{14}+\dfrac{3}{7}\)

\(x-\dfrac{1}{3}=\dfrac{1}{7}+\dfrac{3}{7}\)

\(x-\dfrac{1}{3}=\dfrac{4}{7}\)

\(x=\dfrac{19}{21}\)

x = 19/21 nha

Bài 1

a 2/5+3/6=12/30+15/30=27/30=9/10 .

b 5/9-1/6=30/54-9/54=21/54=7/18

b: =>x/23=1+3/4+4/7=65/28

=>x=23*65/28=1495/28

c: =>3/5:x=3/5-1/4-1/2=9/40

=>x=3/5:9/40=8/3

a, 1,5 +|2x - 2/3| = 3/2

            |2x - 2/3| = 3/2 - 1,5 

            |2x - 2/3| = 0

<=> 2x - 2/3 = 0 

<=> 2x = 0 + 2/3

<=> 2x = 2/3

<=> x = 2/3 : 2

<=> x = 1/3 

Vậy x = 1/3

b, 3/4 - |1/4 - x| = 5/8

            |1/4 - x| = 3/4 - 5/8

            |1/4 - x| = 1/8

<=> 1/4 - x = 1/8

       1/4 - x = /1/8

<=> x = 1/4 - 1/8

       x = 1/4 - ( -1/8)

<=> x = 1/8

       x = 3/8

Vậy x thuộc { 1/8 ; 3/8 }

(x+1)+(x+2)+(x+3)=4x

x+1+x+2+x+3=4x

(x+x+x)+(1+2+3)=4x

x*3+6=4x

6=1*x(bớt cả hai vế đi 3*x)

x=6/1(Tìm thừa số)

x=6

Theo đề ta có : x + 1 chia hết cho 2, 4, 5  và x là số nhỏ nhất hay x + 1 thuộc BCNN(2, 4, 5)

Ta có: 2 = 2 ; 4 = 2²  ; 5 = 5

=> BCNN(2, 4, 5) = 2² . 5 = 20

=> x + 1 = 20 => x = 20 - 1= 19

Vậy x = 19 

x chia 2 dư 1; x chia 4 dư 3; x chia 5 dư 4

\(\Rightarrow x+1\in BC\left(2,4,5\right)=B\left(20\right)=\left\{20;40;...\right\}\)

Mà \(x\) nhỏ nhất nên \(x-1\) nhỏ nhất

\(\Rightarrow x+1=20\Rightarrow x=19\)

Bài 1: 

\(=\dfrac{-3-39}{32}+\dfrac{-6-11}{17}+\dfrac{-1}{6}=-\dfrac{21}{16}+\dfrac{-1}{6}-1=-\dfrac{119}{48}\)

Bài 2: 

\(\Leftrightarrow x:5=-\dfrac{13}{20}\)

hay x=-13/4

\(\frac{3}{13}.\frac{5}{9}+\frac{1}{6}:\frac{13}{3}+1\)

\(=\frac{3}{13}.\frac{5}{9}+\frac{1}{6}.\frac{3}{13}+1\)

\(=\frac{3}{13}.\left(\frac{5}{9}+\frac{1}{6}\right)+1\)

\(=\frac{3}{13}.\left(\frac{30+9}{54}\right)+1\)

\(=\frac{3}{13}.\frac{39}{54}+1\)

\(=\frac{1}{6}+1\)

\(=\frac{7}{6}\)

\(\frac{5}{6}-\frac{7}{9}.\frac{2}{13}-\frac{7}{9}.\frac{11}{13}+\frac{-2}{9}\)

\(=\frac{5}{6}-\frac{7}{9}.\left(\frac{2}{13}-\frac{11}{13}\right)+\frac{-2}{9}\)

\(=\frac{5}{6}-\frac{7}{9}.\frac{-9}{13}-\frac{2}{9}\)

\(=\frac{5}{6}-\frac{-7}{13}-\frac{2}{9}\)

\(\frac{5}{6}-\frac{7}{9}.\frac{2}{13}-\frac{7}{9}.\frac{11}{13}+\frac{-2}{9}\)

\(=\frac{5}{6}-\frac{7}{9}.\left(\frac{2}{13}-\frac{11}{13}\right)+\frac{-2}{9}\)

\(=\frac{5}{6}-\frac{7}{9}.\frac{-9}{13}-\frac{2}{9}\)

\(=\frac{5}{6}-\frac{-7}{13}-\frac{2}{9}\)

\(=\frac{5}{6}+\frac{7}{13}-\frac{2}{9}\)

\(=\frac{195+126-52}{234}\)

\(=\frac{269}{234}\)

\(\frac{3}{13}.\frac{5}{9}+\frac{1}{6}:\frac{13}{3}+1\)

\(=\frac{3}{13}.\frac{5}{9}+\frac{1}{6}.\frac{3}{13}+1\)

\(=\frac{3}{13}.\left(\frac{5}{9}+\frac{1}{6}\right)+1\)

\(=\frac{3}{13}.\left(\frac{30+9}{54}\right)+1\)

\(=\frac{3}{13}.\frac{39}{54}+1\)

\(=\frac{1}{6}+1=\frac{1}{6}+\frac{6}{6}\)

\(=\frac{7}{6}\)

\(\frac{-7}{9}.\frac{2}{13}-\frac{7}{9}.\frac{11}{13}+\frac{-2}{9}\)

\(=\frac{-7}{9}.\frac{2}{13}+\frac{-7}{9}.\frac{11}{13}+\frac{-2}{9}\) 

\(=\frac{-7}{9}.\left(\frac{2}{13}+\frac{11}{13}\right)+\frac{-2}{9}\)

\(=\frac{-7}{9}.1+\frac{-2}{9}\)

\(=\frac{-7}{9}+\frac{-2}{9}\)

\(=\frac{-9}{9}=-1\)

\(\frac{2}{13}.\frac{2}{7}.5\)

\(=\frac{2.2.5}{13.7}\)

\(=\frac{20}{91}\)

\(\frac{1}{5}.\frac{11}{12}.\frac{21}{6}\)

\(=\frac{11.21}{5.12.6}\)

\(=\frac{231}{360}=\frac{77}{120}\)

a) A = 1 + 3 + 3² + ... + 3⁷ 

3A = 3 ( 1 + 3 + 3² + .. + 3⁷)

3A = 3 + 3² + 3³ + ...+ 3⁸

b) Vì 3A = 3 + 3² + 3³ + ...+3⁸

2A = 3⁸- 1

A = ( 3⁸-1) : 2 (Điều phải chứng minh)

a) A = 1 + 3 + 32 + ... + 37 

3A = 3 ( 1 + 3 + 32 + .. + 37)

3A = 3 + 32 + 33 + ...+ 38

b) Vì 3A = 3 + 32 + 33 + ...+38

2A = 38- 1

A = ( 38-1) : 2 (Điều phải chứng minh)

Mong bạn tick cho mình