đề gi rõ ra mới tính được

\(\frac{2}{3}\cdot x:\frac{1}{5}=1\frac{1}{3}:\frac{1}{4}\)

\(\Leftrightarrow\frac{2}{3}\cdot x:\frac{1}{5}=\frac{16}{3}\)

\(\Rightarrow\frac{2}{3}\cdot x=\frac{16}{3}\cdot\frac{1}{5}\)

\(\Rightarrow x=\frac{16}{15}:\frac{2}{3}\)

\(\Rightarrow x=\frac{8}{5}\)

Ta có :

\(\frac{2}{3}x:\frac{1}{5}=1\frac{1}{3}:\frac{1}{4}\)

\(\frac{2}{3}x:\frac{1}{5}=\frac{1}{3}:\frac{1}{4}\)

\(2x:\frac{1}{5}=\frac{4}{3}\)

\(2x=\frac{4}{3}.\frac{1}{5}\)

\(2x=\frac{4}{15}\)

\(x=\frac{4}{15}:2\)

\(\Rightarrow x=\frac{2}{15}\)

\(\frac{3}{4}\)x 8,4 + 2,8 x \(1\frac{1}{2}\)

= 0,75 x 8,4 + 2,8 x \(\frac{3}{2}\)

= 0,75 x 8,4 + 2,8 x 1,5

= 6,3 + 4,2

= 10,5

\(\frac{3}{4}\times8,4+2,8\times1\frac{1}{2}\)

\(=6,3+4,2\)

\(=10,5\)

Kết bạn với mình nha!

cam on cac cau nha 

thanks you very much

B1

B = 5² . 4 - ( 18 + 6 . 7 ) : 81 : 3³

= 25 . 4 - ( 18 + 42 ) : 3⁴ : 3³

= 100 - 60 : 3

= 100 - 20

= 80

B2

5^x+1 + 52 = 6² + ( 7⁹ : 7⁷ - 2³ )

=> 5^x+1 + 52 = 36 + ( 7² - 8 )

=> 5^x+1 + 52 = 36 + 41

=> 5^x+1 + 52 = 77

=> 5^x+1 = 25

=> 5^x+1 = 5²

=> x + 1 = 2

=> x = 1

\(+)18⋮x-3\)

\(\Rightarrow x-3\inƯ\left(18\right)\)

mà \(Ư\left(18\right)=\left\{1;2;3;6;9;18\right\}\)

\(\Rightarrow\hept{\begin{cases}x-3=1;x-3=6\\x-3=2;x-3=9\\x-3=3;x-3=18\end{cases}}\)

\(\Rightarrow\hept{\begin{cases}x=4;x=9\\x=5;x=12\\x=6;x=21\end{cases}}\)

\(26⋮\left(x+1\right)\)

\(\Rightarrow\left(x+1\right)\inƯ\left(26\right)\)

mà \(Ư\left(26\right)=\left\{1;2;13;26\right\}\)

\(\Rightarrow\orbr{\begin{cases}x+1=1\\x+1=2\end{cases}}\orbr{\begin{cases}x+1=13\\x+1=26\end{cases}}\)

\(\Rightarrow\orbr{\begin{cases}x=0\\x=1\end{cases}}\orbr{\begin{cases}x=12\\x=25\end{cases}}\)

`@` `\text {Ans}`

`\downarrow`

`a)`

\(\dfrac{3}{4}+\dfrac{2}{3}+\dfrac{3}{5}\)

`=`\(\dfrac{9}{12}+\dfrac{8}{12}+\dfrac{3}{5}\)

`=`\(\dfrac{17}{12}+\dfrac{3}{5}\)

`=`\(\dfrac{85}{60}+\dfrac{36}{60}\)

`=`\(\dfrac{121}{60}\)

`b)`

\(\dfrac{1}{2}\cdot\dfrac{9}{13}\div\dfrac{27}{26}\)

`=`\(\dfrac{1}{2}\cdot\dfrac{9}{13}\cdot\dfrac{26}{27}\)

`=`\(\dfrac{1}{2}\cdot\dfrac{2}{3}\)

`=`\(\dfrac{1}{3}\)

`c)`

\(\dfrac{2}{7}\cdot\dfrac{1}{9}+\dfrac{2}{7}\cdot\dfrac{2}{9}+\dfrac{1}{3}\cdot\dfrac{5}{7}\)

`=`\(\dfrac{2}{7}\cdot\left(\dfrac{1}{9}+\dfrac{2}{9}\right)+\dfrac{1}{3}\cdot\dfrac{5}{7}\)

`=`\(\dfrac{2}{7}\cdot\dfrac{1}{3}+\dfrac{1}{3}\cdot\dfrac{5}{7}\)

`=`\(\dfrac{1}{3}\cdot\left(\dfrac{2}{7}+\dfrac{5}{7}\right)\)

`=`\(\dfrac{1}{3}\cdot1=\dfrac{1}{3}\)

`d)`

\(11\div\dfrac{5}{2}+11\div\dfrac{7}{3}+11\div\dfrac{35}{6}\)

`=`\(11\cdot\dfrac{2}{5}+11\cdot\dfrac{3}{7}+11\cdot\dfrac{6}{35}\)

`=`\(11\cdot\left(\dfrac{2}{5}+\dfrac{3}{7}+\dfrac{6}{35}\right)\)

`=`\(11\cdot1=11\)

a) 3/4 + 2/3 + 3/5 = 45/60 + 40/60 + 36/60 = 121/60

b) 1/2 x 9/13 : 27/26 = 9/26 x 26/27 = 1/3

c) 2/7 x 1/9 + 2/7 x 2/9 + 1/3 x 5/7 = 2/7 x (1/9 + 2/9) + 5/21 = 2/7 x 1/3 + 5/21 = 2/21 + 5/21 = 1/3

d) 11 : 5/2 + 11 : 7:3 + 11 : 35/6 = 11 x (2/5 + 3/7 + 6/35) = 11 x 1 = 11 

Bài 1:

a: \(=25\cdot4-\left(18+42\right):81:27\)

\(=100-\dfrac{20}{729}=\dfrac{72880}{729}\)

b: \(=\left(1-24\right)\cdot3+2^5-97=-69+32-97=-134\)

a) 3(x - 1) - 1 = 26

=> 3x - 3 = 26 + 1

=> 3x - 3 = 27

=> 3x = 27 + 3

=> 3x = 30

=> x = 30 : 3

=> x = 10

b) |x + 4| - 9 = (-2)³

=> |x + 4| - 9 = -8

=> |x + 4| = -8 + 9

=> |x + 4| = 1

=> \(\orbr{\begin{cases}x+4=1\\x+4=-1\end{cases}}\) 

=> \(\orbr{\begin{cases}x=-3\\x=-5\end{cases}}\)

Vậy ...

c) 2x - 5 \(⋮\)x - 1

<=> 2(x - 1) - 3 \(⋮\)x - 1

<=> 3 \(⋮\)x - 1

<=> x - 1 \(\in\)Ư(3) = {1; -1; 3; -3}

Lập bảng :

Vậy ...

a) 3×(x-1) - 1 =26

    => 3×(x-1) = 26+1

    => 3×(x-1) = 27

    => x-1 = 27:3

    => x-1 = 9

    => x= 9+1 

    => x= 10

b) |x+4| - 9 = (-2)^3

   = | x+4| - 9 = -8

   = | x+4| = (-8)+9

   = | x+4| =1

  => x+4= 1 hay x+4= (-1)

Khi x+4= 1

      => x= 1-4

      => x= -3

Khi x+4= (-1)

      => x= (-1)+4

      => x= -5

Vậy: x= -3 hoặc x= -5

Bài 1 :

\(A=3^0+3^1+3^2+3^3+...+3^{98}\)

\(A=\left(1+3+3^2\right)+.....+\left(3^{97}+3^{98}+3^{99}\right)\) ( Nhóm 3 số 1 nhé )

\(A=13+.....+3^{97}.13⋮13\left(\text{đ}pcm\right)\)

Bài 2 :

Theo ý a ta có : 

\(A=13+.....+3^{97}.13+3^{99}+3^{100}\)

\(A=13+.....+3^{97}.13+3^{99}.4⋮̸13\)

Bài 3 :

Để D chia hết cho 2 thì x chia hết cho 2

1. \(A=3^0+3^1+3^2+...+3^{98}\)

\(=\left(1+3+3^2\right)+\left(3^3+3^4+3^5\right)+...+\left(3^{96}+3^{97}+3^{98}\right)\)

\(=\left(1+3+3^2\right)+3^3\left(1+3+3^2\right)+...+3^{96}\left(1+3+3^2\right)\)

\(=13\left(1+3^3+...+3^{96}\right)\)chia hết cho \(13\).

2. \(B=3^0+3^1+3^2+3^3+...+3^{100}\)

\(=1+3+\left(3^2+3^3+3^4\right)+...+\left(3^{98}+3^{99}+3^{100}\right)\)

\(=4+3^2\left(1+3+3^2\right)+...+3^{98}\left(1+3+3^2\right)\)

\(=4+13\left(3^2+3^5+...+3^{98}\right)\)không chia hết cho \(13\).

3. \(D=\left(12.3+26.b+2022.c+x\right)\)chia hết cho \(2\)

\(\Leftrightarrow x⋮2\)(vì \(12.3⋮2,26b⋮2,2022c⋮2\))