7 x 2 = 14       7 x 4 = 28       7 x 6 = 42       7 x 3 = 21

2 x 7 = 14       4 x 7 = 28       6 x 7 = 42       3 x 7 = 21

14 : 7 = 2       28 : 7 = 4       42 : 7 = 6       21 : 7 = 3

14 : 2 = 7       28 : 4 = 7       42 : 6 = 7       21 : 3 = 7

nhiều quá :((

\(a,2\left(x-5\right)-3\left(x+7\right)=14\)

\(2x-10-3x-21=14\)

\(-x-31=14\)

\(-x=45\)

\(x=45\)

\(b,5\left(x-6\right)-2\left(x+3\right)=12\)

\(5x-30-2x-6=12\)

\(3x-36==12\)

\(3x=48\)

\(x=16\)

\(c,3\left(x-4\right)-\left(8-x\right)=12\)

\(3x-12-8+x=0\)

\(4x-20=0\)

\(4x=20\)

\(x=5\)

Cố nốt nha bn ! 

cảm ơn, bn nha:)))

mà hình như bạn TOP 3 trả lời câu hỏi pải ko nhỉ???

d, \(-7\left(3x-5\right)+2\left(7x-14\right)=28\)

\(\Leftrightarrow-21x+35+14x-28=28\Leftrightarrow-7x=21\Leftrightarrow x=-3\)

e, \(5\left(3-2x\right)+5\left(x-4\right)=6-4x\)

\(\Leftrightarrow15-6x+5x-20=6-4x\Leftrightarrow-5-x=6-4x\)

\(\Leftrightarrow-11+3x=0\Leftrightarrow x=\frac{11}{3}\)

f, \(-5\left(2-x\right)+4\left(x-3\right)=10x-15\)

\(\Leftrightarrow-10+5x+4x-12=10x-15\Leftrightarrow-22+9x=10x-15\)

\(\Leftrightarrow-7-x=0\Leftrightarrow x=-7\)

Học sinh nhẩm và ghi kết quả như sau:

3 x 4 = 12    2 x 6 = 12     4 x 3 = 12    5 x 6 = 30

3 x 7 = 21    2 x 8 = 16     4 x 7 = 28    5 x 4 = 20

3 x 5 = 15   2 x 4 = 8        4 x 9 = 36    5 x 7 = 35

3 x 8 = 24    2 x 9 = 18     4 x 4 = 16    5 x 9 = 45

3 x4 = 12

3 x7 = 21

3 x5 = 15

3 x8 =24

2 x 6= 12

2 x8 = 16

2 x4 =8

2 x9 =18

4 x3 =12

4 x7 =28

4 x9 =36

4 x4 =16

5 x6 =30 

5 x4 =20

5 x7 =35

5 x9 =45

3 x 4 = 12    2 x 6 = 12     4 x 3 = 12    5 x 6 = 30

3 x 7 = 21    2 x 8 = 16     4 x 7 = 28    5 x 4 = 20

3 x 5 = 15   2 x 4 = 8        4 x 9 = 36    5 x 7 = 35

3 x 8 = 24    2 x 9 = 18     4 x 4 = 16    5 x 9 = 45

7 x 2 = 14

4 x 7 = 28

7 x 6 = 42

3 x 7 = 21

5 x 7 = 35

2 x 7 = 14

7 x 4 = 28

6 x 7 = 42

7 x 3 = 21

7 x 5 = 35

7 x 2 = 14

4 x 7 = 28

7 x 6 = 42

3 x 7 = 21

5 x 7 = 35

2 x 7 = 14

7 x 4 = 28

6 x 7 = 42

7 x 3 = 21

7 x 5 = 35

\(1,\\ x+\dfrac{1}{2}=-\dfrac{5}{3}\\ x=-\dfrac{5}{3}-\dfrac{1}{2}\\ x=-\dfrac{13}{6}\\ Vậyx=-\dfrac{13}{6}\)

\(2,\\ \dfrac{1}{3}-x=\dfrac{3}{5}\\ x=\dfrac{1}{3}-\dfrac{3}{5}\\ x=-\dfrac{4}{15}\\ Vậyx=-\dfrac{4}{15}\)

\(3,\\ 3-4+x=\dfrac{7}{2}\\ -1+x=\dfrac{7}{2}\\ x=\dfrac{7}{2}+1\\ x=\dfrac{9}{2}\\ Vậyx=\dfrac{9}{2}\)

\(4,\\ x-\dfrac{4}{3}=-\dfrac{7}{9}\\ x=-\dfrac{7}{9}+\dfrac{4}{3}\\ x=\dfrac{15}{27}\\ Vậyx=\dfrac{15}{27}\)

\(5,\\ x-\left(-\dfrac{7}{3}\right)=\dfrac{5}{6}\\ x=\dfrac{5}{6}-\dfrac{7}{3}\\ x=-\dfrac{27}{18}\\ Vậyx=-\dfrac{27}{18}\)

\(6,\\ x-\dfrac{1}{5}=\dfrac{9}{10}\\ x=\dfrac{9}{10}+\dfrac{1}{5}\\ x=\dfrac{11}{10}\\ Vậyx=\dfrac{11}{10}\)

\(7,\\ x+\dfrac{5}{12}=\dfrac{3}{8}\\ x=\dfrac{3}{8}-\dfrac{5}{12}\\ x=-\dfrac{1}{24}\\ Vậyx=-\dfrac{1}{24}\)

\(8,\\ x+\dfrac{5}{4}=\dfrac{7}{6}\\ x=\dfrac{7}{6}-\dfrac{5}{4}\\ x=-\dfrac{9}{24}\\ Vậyx=-\dfrac{9}{24}\)

\(9,\\ x-\dfrac{2}{7}=\dfrac{1}{35}\\ x=\dfrac{1}{35}+\dfrac{2}{7}\\ x=\dfrac{11}{35}\\ Vậyx=\dfrac{11}{35}\\ 10,\\ x-\dfrac{1}{5}=-\dfrac{7}{10}\\ x=-\dfrac{7}{10}+\dfrac{1}{5}\\ x=-\dfrac{1}{2}\\ Vậyx=-\dfrac{1}{2}\)

ahiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiii hãy ấn a

1/ 10(X-7)-8(X+5)=6(-5)+24
10x - 70 - 8x - 40 = -30 +24
2x - 110 = -6
2x = 104
x=52

2/ 8(X-|-7|)-6(X-2)=|-8|.6-50
8(x - 7) - 6(x-2) = 8.6 - 50
8x - 56 - 6x +12 =48 -50
2x - 44 = -2
2x = 42
x=21

3/ 2(4X-8)-7(3+X)=|-4|(3-2)
8x-16 - 21 - 7x = 4.1
x-37=4
x=41

4/ 12(X-4)=6(x-2)-16(X+3)=7|-4|
12x - 48 = 6x - 12 - 16x -48 =7.4
12x - 48 = 28
12x=76
x=19/3

5/ 4(X-5)-7(5-X)+10(5-X)=-3
4x - 20 -35 +7x + 50 -10x = -3
x - 5 = -3
x = -2
Chúc bạn học tốt!

1x2= 2       1x2x3=6             1x2x3x4=24               1x2x3x4x5=120            1x2x3x4x5x6=720                   1x2x3x4x5x6x7=5040 

1x2x3x4x5x6x7x8=40320                 1x2x3x4x5x6x7x8x9=362880           1x2x3x4x5x6x7x8x9x10=3628800

1 x 2 = 2

1 x 2 x 3 = 6

1 x 2 x 3 x 4 = 24

1 x 2 x 3 x 4 x 5 = 120

1 x 2 x 3 x 4 x 5 x 6 = 720

1 x 2 x 3 x 4 x 5 x 6 x 7 = 5040

1 x 2 x 3 x 4 x 5 x 6 x 7 x 8 = 40320

1 x 2 x 3 x 4 x 5 x 6 x 7 x 8 x 9 = 362880

1 x 2 x 3 x 4 x 5 x 6 x 7 x 8 x 9 x 10 = 3628800

1 . 2 = 2

1 .2 .3 = 6

1 .2 .3 .4 = 24

1 .2 .3 .4 .5 = 120

1 .2 .3 .4 .5 .6 = 720

1 .2 .3 .4 .5 .6 .7 = 5040

1 .2 .2 .4 .5 .6 .7 .8 = 40320

1 .2 .3 .4 .5 .6 .7 .8 .9 =362880

1 .2 .3 .4 .5 .6 .7 .8 .9 .10 = 3628800

          hok tốt

1/   Suy ra: -35 + 7x - 2x + 20 = 15

                5x - 15 = 15

                 5x = 30

                  x = 6

2/  Suy ra:  4x - 20 - 3x - 21 = -19

                   x - 41  = -19

                    x  = 22

3/   Suy ra:   8 - 4x + 3x - 15 = 14

                    -7 -x = 14

                      x = -7 -14

                      x = -21

4/    Suy ra:   7x - 63 - 30 + 5x = -6 + 11x

                      7x + 5x - 11x = -6 +63 + 30

                       x   =    87

5/    Suy ra:  -21x +35 + 14x - 28 = 28

                       -21x + 14x = 28 +28 - 35

                         -7x = 21

                             x= -3

6/     Suy ra:  20 - 5x + 7x - 14 = -2

                        2x   =   -8

                          x = -4

7/    Suy ra:   4x +15 -5x = 7

                      -x = -8

                        x = 8

 8/   Suy ra:   5x - 35 +30 -10x = 20

                      -5x - 5 = 20

                          -5x = 25

                            x = -5

9/    Suy ra:     35 - 7x + 5x - 10 = 15

                         -7x + 5x = 15 +10 - 35

                        -2x = -10

                          x = 5

b: \(x+\dfrac{5}{6}=\dfrac{3}{8}\)

=>\(x=\dfrac{3}{8}-\dfrac{5}{6}\)

=>\(x=\dfrac{9}{24}-\dfrac{20}{24}=-\dfrac{11}{24}\)

c: \(\dfrac{2}{3}x-\dfrac{1}{2}=\dfrac{5}{6}\)

=>\(\dfrac{2}{3}x=\dfrac{5}{6}+\dfrac{1}{2}=\dfrac{8}{6}=\dfrac{4}{3}\)

=>2x=4

=>x=4/2=2

d: \(\dfrac{x}{7}=\dfrac{6}{-21}\)

=>\(\dfrac{x}{7}=\dfrac{-2}{7}\)

=>x=-2

e: \(\left(\dfrac{7}{3}x-0,6\right):\dfrac{3^2}{5}=1\)

=>\(\dfrac{7}{3}x-0,6=\dfrac{3^2}{5}=1,8\)

=>\(\dfrac{7}{3}x=2,4\)

=>\(x=2,4:\dfrac{7}{3}=2.4\cdot\dfrac{3}{7}=\dfrac{7.2}{7}=\dfrac{36}{35}\)

f: \(\dfrac{x}{45}=\dfrac{5}{6}+\dfrac{-29}{30}\)

=>\(\dfrac{x}{45}=\dfrac{25}{30}-\dfrac{29}{30}=-\dfrac{4}{30}=-\dfrac{2}{15}\)

=>\(x=-\dfrac{2}{15}\cdot45=-6\)

g: \(\left(4,5-2x\right)\cdot\left(-\dfrac{1^4}{7}\right)=\dfrac{11}{14}\)

=>\(4,5-2x=\dfrac{11}{14}:\dfrac{-1}{7}=\dfrac{-11}{2}\)

=>\(2x=4,5+\dfrac{11}{2}=\dfrac{20}{2}=10\)

=>x=10/2=5

h: \(-\dfrac{2}{7}+\dfrac{4}{7}x=\dfrac{5}{7}\)

=>\(\dfrac{4}{7}x=\dfrac{5}{7}+\dfrac{2}{7}=\dfrac{7}{7}\)

=>4x=7

=>\(x=\dfrac{7}{4}\)

a: =>x=3/7+3/5=15/35+21/35=36/35

b: =>x/35=4/5-5/7=28/35-25/35=3/35

=>x=3

c: =>x<3/4+8/4=11/4

=>\(x\in\left\{0;1;2;3\right\}\)

d: =>5/3<x<5/6+24/6=29/6

=>\(x\in\left\{2;3;4\right\}\)

e: =>x<10/12-9/12=1/12

=>x=0

f: =>2/3<x<12/6-5/6=7/6

=>x=1