a,sửa đề : đk x khác -2;  2 

 \(x^2+x-2+5x-10=12+x^2-4\)

\(\Leftrightarrow6x-20=0\Leftrightarrow x=\dfrac{10}{3}\left(tm\right)\)

b, \(3x-12+5+5x=105\Leftrightarrow8x=112\Leftrightarrow x=14\)

c, \(3x^2+14x-49=-\left(x^2+2x-15\right)\)

\(\Leftrightarrow4x^2+16x-34=0\Leftrightarrow x=\dfrac{-4\pm5\sqrt{2}}{2}\)

a. ko hỉu đề lắm :v

b.\(\dfrac{x-4}{5}+\dfrac{1+x}{3}=7\)

\(\Leftrightarrow\dfrac{3\left(x-4\right)+5\left(1+x\right)}{15}=\dfrac{105}{15}\)

\(\Leftrightarrow3\left(x-4\right)+5\left(1+x\right)=105\)

\(\Leftrightarrow3x-12+5+5x-105=0\)

\(\Leftrightarrow8x-112=0\)

\(\Leftrightarrow8x=112\)

\(\Leftrightarrow x=14\)

c.\(\left(3x-7\right)\left(x+7\right)=\left(5+x\right)\left(3-x\right)\)

\(\Leftrightarrow3x^2+21x-7x-49=15-5x+3x-x^2\)

\(\Leftrightarrow4x^2+16x-64=0\)

Nghiệm xấu lắm bạn

1) = \(\frac{3}{5}\)

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

3)\(\frac{9}{13}\)

4)\(\frac{4}{13}\)

viết p/s như nào vậy bạn

= 51/20

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= 3/14

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= 4/7 - 2/7 

= 2/7

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= 17/45

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= 2/3 

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= 2 x 1/4 

= 1/2

\(\left(x-\dfrac{4}{7}\right):-\dfrac{1}{3}=1\)
\(\Rightarrow x-\dfrac{4}{7}=1\cdot-\dfrac{1}{3}\)

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

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

\(\Rightarrow x=\dfrac{5}{12}\)

___________________

\(\dfrac{2}{3}-\dfrac{7}{4}:x=\dfrac{5}{6}\)

\(\Rightarrow\dfrac{7}{4}:x=\dfrac{2}{3}-\dfrac{5}{6}\)

\(\Rightarrow\dfrac{7}{4}:x=-\dfrac{1}{6}\)

\(\Rightarrow x=\dfrac{7}{4}:-\dfrac{1}{6}\)

\(\Rightarrow x=-\dfrac{21}{2}\)

(x - 4/7) : (-1/3) = 1

x - 4/7 = -1/3

x = -1/3 +4/7

x = 5/21

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2/3 + 7/4 : x = 5/6

7/4 : x = 5/6 - 2/3

7/4 : x = 1/6

x = 7/4 : 1/6

x = 21/2

a) ( x - 4/7) : (-1/3) = 1

      x- 4/7                = 1 . (-1/3)

         x                     =-1/3 + 4/7

         x                     =   5/12

b) 2/3 + 7/4 : x = 5/6

              7/4: x  = 2/3 -5/6

                     x   = 7/4  : (-1/6 )

                     x    =    -21/2

a) 3/8 . x = 9/8 - 1

3/8 . x = 1/8

x = 1/8 : 3/8

x = 1/3

b) 4/5 . x = 7/5 - 1/5

4/5 . x = 6/5

x = 6/5 : 4/5

x = 3/2

c) 12/7 : x + 2/3 = 7/5

12/7 : x = 7/5 - 2/3

12/7 : x = 11/15

x = 12/7 : 11/15

x = 180/77

d) 3.(x + 7) - 15 = 27

3.(x + 7) = 27 + 15

3.(x + 7) = 42

x + 7 = 42 : 3

x + 7 = 14

x = 14 - 7

x = 7

a) \(\dfrac{3}{8}x=\dfrac{9}{8}-1\)

\(\Rightarrow\dfrac{3}{8}x=\dfrac{1}{8}\)

\(\Rightarrow x=\dfrac{1}{8}:\dfrac{3}{8}=\dfrac{1}{3}\)

b) \(\dfrac{4}{5}x=\dfrac{7}{5}-\dfrac{1}{5}\)

\(\Rightarrow\dfrac{4}{5}x=\dfrac{6}{5}\)

\(\Rightarrow x=\dfrac{6}{5}:\dfrac{4}{5}=\dfrac{3}{2}\)

c) \(\dfrac{12}{7}:x+\dfrac{2}{3}=\dfrac{7}{5}\)

\(\Rightarrow\dfrac{12}{7}:x=\dfrac{7}{5}-\dfrac{2}{3}\)

\(\Rightarrow\dfrac{12}{7}:x=\dfrac{11}{15}\)

\(\Rightarrow x=\dfrac{12}{7}:\dfrac{11}{15}=\dfrac{180}{77}\)

d) \(3\left(x+7\right)-15=27\)

\(\Leftrightarrow3\left(x+7\right)=42\)

\(\Leftrightarrow x+7=14\Leftrightarrow x=7\)

\(3\cdot\left(\dfrac{1}{2}-x\right)-5\left(x-\dfrac{1}{10}\right)=-\dfrac{7}{4}\\ \Leftrightarrow-8x=-\dfrac{15}{4}\\ \Leftrightarrow x=\dfrac{15}{32}\)

\(4\left(\dfrac{3}{4}+x\right)-\dfrac{1}{5}=7x-\dfrac{1}{7}\\ \Leftrightarrow3x=\dfrac{103}{35}\\ \Leftrightarrow x=\dfrac{103}{105}\)

\(3\left(\dfrac{1}{2}-x\right)-5\left(x-\dfrac{1}{10}\right)=-\dfrac{7}{4}\)

\(\Rightarrow\dfrac{3}{2}-3x-5x+\dfrac{1}{2}=-\dfrac{7}{4}\)

\(\Rightarrow2-8x=-\dfrac{7}{4}\)

\(\Rightarrow8x=2+\dfrac{7}{4}\)

\(\Rightarrow8x=\dfrac{15}{4}\)

\(\Rightarrow x=\dfrac{15}{32}\)

___________

\(4\left(\dfrac{3}{4}+x\right)-\dfrac{1}{5}=7x-\dfrac{1}{7}\)

\(\Rightarrow3+4x-\dfrac{1}{5}=7x-\dfrac{1}{7}\)

\(\Rightarrow4x+\dfrac{14}{5}=7x-\dfrac{1}{7}\)

\(\Rightarrow7x-4x=\dfrac{14}{5}+\dfrac{1}{7}\)

\(\Rightarrow3x=\dfrac{103}{35}\)

\(\Rightarrow x=\dfrac{103}{105}\)

`3(1/2 - x) - 5(x -1/10) = -7/4`

`=> 3/2 - 3x - 5x + 1/2 = -7/4`

`=> (-3x- 5x) + (3/2 + 1/2) = -7/4`

`=> -8x + 2 = -7/4`

`=>   -8x     = -15/4`

`=>      x     = 15/32`

`4(3/4 + x) - 1/5 = 7x - 1/7`

`=> 3 + 4x - 1/5 = 7x - 1/7`

`=> 4x + (3- 1/5) = 7x - 1/7`

`=> 4x + 14/5     = 7x - 1/7`

`=> 4x - 7x         = -14/5 - 1/7`

`=> -3x              = -103/35`

`=>    x              = 103/105`

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!