\(=6\sqrt{5}+21\sqrt{5}-12\sqrt{5}+16\sqrt{5}+50\sqrt{5}=81\sqrt{5}\)

Bài 1:

a) \(\dfrac{9}{20}-\dfrac{8}{15}\times\dfrac{5}{12}\)

\(=\dfrac{9}{20}-\dfrac{2}{9}\)

\(=\dfrac{41}{180}\)

b) \(\dfrac{2}{3}\div\dfrac{4}{5}\div\dfrac{7}{12}\)

\(=\dfrac{2}{3}\times\dfrac{5}{4}\times\dfrac{12}{7}\)

\(=\dfrac{5}{6}\times\dfrac{12}{7}\)

\(=\dfrac{10}{7}\)

c) \(\dfrac{7}{9}\times\dfrac{1}{3}+\dfrac{7}{9}\times\dfrac{2}{3}\)

\(=\dfrac{7}{9}\times\left(\dfrac{1}{3}+\dfrac{2}{3}\right)\)

\(=\dfrac{7}{9}\times1\)

\(=\dfrac{7}{9}\)

Bài 2:

a) \(2\times\left(x-1\right)=4026\)

\(\left(x-1\right)=4026\div2\)

\(x-1=2013\)

\(x=2014\)

Vậy: \(x=2014\)

b) \(x\times3,7+6,3\times x=320\)

\(x\times\left(3,7+6,3\right)=320\)

\(x\times10=320\)

\(x=320\div10\)

\(x=32\)

Vậy: \(x=32\)

c) \(0,25\times3< 3< 1,02\)

\(\Leftrightarrow0,75< 3< 1,02\) ( S )

=> \(0,75< 1,02< 3\)

1) \(2^3\times x-5^2\times x=2\times\left(5^2+2^2\right)-33\)

\(x\times\left(2^3-5^2\right)=2\times\left(25+4\right)-33\)

\(x\times\left(8-25\right)=2\times29-33\)

\(x\times-17=25\)

\(x=-\dfrac{25}{17}\)

2) \(15\div\left(x+2\right)=\left(3^3+3\right)\div1\)

\(15\div\left(x+2\right)=\left(27+3\right)\div1\)

\(15\div\left(x+2\right)=30\div1\)

\(15\div\left(x+2\right)=30\)

\(x+2=\dfrac{1}{2}\)

\(x=-\dfrac{3}{2}\)

3) \(20\div\left(x+1\right)=\left(5^2+1\right)\div13\)

\(20\div\left(x+1\right)=\left(25+1\right)\div13\)

\(20\div\left(x+1\right)=26\div13\)

\(20\div\left(x+1\right)=2\)

\(x+1=20\div2\)

\(x+1=10\)

\(x=9\)

4) \(320\div\left(x-1\right)=\left(5^3-5^2\right)\div4+15\)

\(320\div\left(x-1\right)=\left(125-25\right)\div4+15\)

\(320\div\left(x-1\right)=100\div4+15\)

\(320\div\left(x-1\right)=25+15\)

\(320\div\left(x-1\right)=40\)

\(x-1=8\)

\(x=9\)

5) \(240\div\left(x-5\right)=2^2\times5^2-20\)

\(240\div\left(x-5\right)=4\times25-20\)

\(240\div\left(x-5\right)=100-20\)

\(240\div\left(x-5\right)=80\)

\(x-5=30\)

\(x=35\)

6) \(70\div\left(x-3\right)=\left(3^4-1\right)\div4-10\)

\(70\div\left(x-3\right)=\left(81-1\right)\div4-10\)

\(70\div\left(x-3\right)=80\div4-10\)

\(70\div\left(x-3\right)=20-10\)

\(70\div\left(x-3\right)=10\)

\(x-3=7\)

\(x=10\)

bạn hình như viết sai đề

A=17/8

B=-2

C=74

(x-14)-20=5

=> x-14 = 25

=> x = 39

Các dạng toán như này lớp 6 ai cũng làm được cả * lười vừa thôi*

( x - 14 ) - 20 = 5

 x - 14 = 5 + 20

 x - 14 = 25

 x = 25 + 14

 x = 39

128 + ( 202 - x ) = 330

           [ 202 - x ] = 330 - 128

             202 - x = 202

                      x = 202 - 202

                      x = 0

( x - 120 ) x 9 = 450

[ x - 120 ] = 450 : 9

 x - 120 = 50

 x = 50 + 120

 x = 170

x - 320 : 32 = 25 x 16

x - 320 : 32 = 400

x - 320 = 400 x 32

x - 320 = 12800

x = 12800 + 320

x = 13120

25 - ( 2x +10 ) = 5

        [ 2x + 10] = 25 - 5

          2x + 10 = 20

          2x = 20 - 10

          2x = 10

            x = 10 : 2

            x = 5

315 - ( 135 - x ) = 215

          [ 135 - x ] = 315 - 215

          [ 135 - x ] = 100

                      x = 135 - 100

                      x = 35

x : 2 + 21 : 3 = 37

x : 2 + 21 = 37 x 3

x : 2 + 21 = 111

x : 2 = 111 - 21

x : 2 = 90

x = 90 x 2

x = 180

4 x ( x + 100 ) = 800

      [ x + 100 ] = 800 : 4

      [ x + 100 ] = 200

       x = 200 - 100

       x = 100

504 : ( 16 - 5x ) = 72

          [ 16 - 5x ] = 504 : 72

           [ 16 - 5x ] = 7

                     5x = 16 - 7

                     5x = 9

                       x = \(\dfrac{9}{5}\)

( x - 5 ) : 7 + 3 = 20

[ x - 5 ] : 7 = 20 - 3

[ x - 5 ] : 7 = 17

[ x - 5 ] = 17 x 7

 x - 5 = 119

 x = 119 + 5

 x = 124